Compounds 15α-hydroxy-tingenone (30), 15-dehydro-pristimerin (31), vitideasin (32) and 20β-hydroxy-scutione (33) were separated from the roots of M. vitis-idaea [24]. Six new compounds, including 7-oxo-7, 8-dihydro-scutione (34), 6,23-dioxo-7,8-dihydro-pristimerol-23-oic Acid (35), 23-nor-blepharodol (36), 3-methoxy-6-oxo-tingenol-23-oic Acid (37), retusonine (38) and 21-Oxopristimerine (39) were isolated from the root bark of M. retusa [25]. A new compound 3-O-Methyl-6-oxo-pristimerol (40) has been isolated from the hexane/Et₂O 1:1 extract of the root bark of M. chubutensis [26]. Compounds 3β,24-epoxy-2α,3α-dihydroxy-D:A-friedooleanan-29-oic acid methyl ester (41), 2α-acetoxy-3β,24-epoxy-3α-hydroxy-D:A-friedooleanan-29-oic acid methyl ester (42), 3α-hydroxy-D:A-friedooleanan-28-oic acid (43) and 3-oxo-D:A-friedooleanan-28,30-olide (44) were obtained from the root bark of M. jelskii [27]. Compounds 3β,11β-dihydroxyfriedelane (45) and 3,4-seco-friedelan-3,11β-olide (46) have been obtained from the hexane extracts of the leaves of M. robusta [28], while (16β)-16-hydroxy-pristimerin (47) was from M. salicifolia [29]. A new triterpenoid, 12,16-dihydroxyfriedelan-3-one (48), was isolated from an ethyl acetate extract of M. oblongata [30]. Compounds 3β,24β-epoxy-29-methoxy-2α,3α,6α-trihydroxy-D:A-friedelane (49) and 3β,24β-epoxy-29-methoxy-2α,3α,6α-triacetoxy-D:A-friedelane (49a) were obtained from the root bark extracts of M. cuzcoina [31]. Three new pentacyclic triterpenoids, friedel-1-en-3,16-dione (50), 1α,29-dihydroxyfriedelan-3-one (51) and 16β,28,29-trihydroxyfriedelan-3-one (52) have been separated from M. robusta [32]. Dispemroquinone (53) was isolated from M. dispermus [33]. A new norquinonemethide triterpene with a netzahualcoyene type skeleton, scutione (54), was isolated from the root bark of M. scutioides [34]. Compounds zeylasterone (55) and demethylzeylasterone (56) were obtained from M. blepharodes [35], and compound 3,15-dioxo-21α-hydroxy friedelane (57) was isolated from the methanol extracts of M. robusta [36]. Maytenfoliol (58) was separated from M. diversifolium [37]. Four new cytotoxic triterpenoid dimers, including cangorosin A (59), atropcangorosin A (60), dihydroatropcangorosin A (61) and cangorosin B (62) were obtained from the extracts of M. ilicifolia [38]. Two new triterpenes, umbellatin α (63) and umbeilatin β (64), have been separated from M. umbellata [39]. Two novel trimer triscutins, A and B (65–66), have been isolated from extracts of the root bark of M. scutioides [40]. Four new triterpene dimers, xuxuarine Eα (67), scutionin αB (68), 6′,7′-dihydro-scutionin αB (69) and 6′β-methoxy-6′,7′dihydro-scutionin αB (70), have been isolated from the extracts of the roots of M. blepharodes and M. magellanica ^[41][42][41,42] (Table 1 and Figure 1).

Figure 1. Twenty-five types (A1–A25) of friedelane triterpenoids skeletons.

Table 1. The friedelane triterpenes isolated from Maytenus.

No.	Name	R1	R2	R3	R4	R5	R6	R7	R8	Type	Ref.
1	Pristimerin	H	H	COOMe	H	H	-	-	-	A1	[16]

β-3,4-Secolup-20(29)-en-3-oic acid (89), were obtained from the aerial parts of M. apurimacensis [48], while compound 3-(E)-β-coumaroylnepeticin (90) was isolated from M. retusa [25]. Compound 3,4-seco-lupa-4(23): 20(29)-diene-3,28-dioic acid 28-methyl ester (91) has been separated from the hexane/Et₂O 1:1 extracts of the root barks of M. magellanica [26]. 1β-Hydroxy-3β-caffeate lup-20(29)-ene (92) was isolated from the roots of M. apurimacensis [49]. Compounds 3-oxo-21β-H-hop-22(29)-ene (93), 3β-hydroxy-21β-H-hop-22(29)-ene (94) and 3,4-seco-21β-H-hop-22(29)-en-3-oic acid (95) were isolated from the leaves of M. robusta [28] (Table 2 and Figure 2).

Figure 2. Seven types (B1–B7) of lupane triterpenes skeletons.

Table 2. The lupane triterpenes isolated from Maytenus.

No.	Name	R1	R2	R3	R4	R5	R6	R7	R8	R9	Type	Ref
71	3β,28,30-Lup-20(29)-ene triol	H	H	OH	CH3	H	H	H	CH2OH	CH2OH	B1	[43]	2	15α-hydroxy-21-keto-pristimerine	α-OH	H	COOMe	=O	H	-	-	-	A1
72	28,30-Dihyroxylup-20(29)-ene-3-one	[	H	17	]
H	=O	CH3	H	H	H	CH2OH	CH2OH	B1	[43]	3
73
-
H
-hop-22(29)-ene
β
-OH
-
-
-
-
-	-	-	-	B6	[	28	]
95	3,4-seco-21β-H-hop-22(29)-en-3-oic acid	-	-	-	-	-	-	-	-	-	B7	[28]

2.1.3. Oleanane Triterpenes

Oleanane triterpenes are widely distributed in the plant kingdom. The configuration of the rings is A/B, B/C and C/D, and they are all of the trans configuration, while the D/E ring is cis. There are eight methyl groups on the core nuclei, and the methyl groups at positions C-10, C-8 and C-17 are all β configuration. The methyl group at the C-14 position is α configuration, while the C-4 and C-20 positions each have two methyl groups. There may also be other substituents present in the molecule. Two new oleanane triterpenes, 3β,19α-dihydroxyolean-12-en-29-oic acid (96) and 3α,19α-dihydroxyolean-12-en-29-oic acid (97), were obtained from M. austyoyunnanensis [14]. Compound 3-oxo-11α-methoxyolean-12-ene (98) was obtained from the extracts of the roots of M. spinosa [24], while 22α-hydroxy-29-methoxy-3β-tetradecanoate-olean-12-ene (99) was separated from the root bark extracts of M. cuzcoina [31]. The new compound maytefolin B (100) was separated from the leaves of a Brazilian medicinal plant, M. ilicifolia [44]. One new triterpene, 3β-peroxy-7β,25-epoxy-D:B-friedoolean-5-ene (101), was separated from the aerial parts of M. apurimacensis [48]. Compounds krukovines A (28-hydroxyolean-12-ene-3,11-dione) (102) and krukovines C (6β,28-dihydroxyolean-12-ene-3,11-dione) (103) have been obtained from a South American medicinal plant known as “chuchuhuasi” (M. krukovii) [50]. The aerial parts of M. undata yielded four new 12-oleanene and 3,4-seco-12-oleanene triterpene acids, namely, 3-oxo-11α-methoxyolean-12-ene-30-oic acid (104), 3-oxo-11α-hydroxyolean-12-ene-30-oic acid (105), 3-oxo-olean-9(11), 12-diene-30-oic acid (106) and 3,4-seco-olean-4(23), 12-diene-3,29-dioic acid (107) [51], while 3α-22β-dihydroxyolean-12-en-29-oicacid (108) was obtained from the methanol extracts of the barks of M. laevis [52]. Compound olean-9(11):12-dien-3β-ol (109) was isolated from the roots of M. acanthophylla [53] and compound 3β-hydroxy-D:B-friedo-olean-5-ene (110) was isolated from M. salicifolia Reissek [54]. Compound 19α-hydroxy-3-olean-12-en-29-oic acid (111) was isolated from M. austyoyunnanensis [55] (Table 3 and Figure 3).

Figure 3. Six types (C1–C6) of oleanane triterpenes skeletons.

Table 3. The oleanane triterpenes isolated from Maytenus.

No.	Name	R1	R2	R3	R4

Table 4. The other triterpenes isolated from Maytenus.

No.	Name	R1	R2R5	RR6	3R7	R4R8	Type	Ref.
Type	Ref.
96	3β,19α-dihydroxyolean-12-en-29-oic acid	β-OH	H	H	CH3	H	α-OH	CH
112	3	COOH	C1	3-Oxo-methoxyurs-12-ene	=O	H	α-OCH3	CH3[14]
D1	[	24	]	97	3α,19α-dihydroxyolean-12-en-29-oic acid	α-OH	H	H	CH3	H
113	Krukovines B	α	=O	-OH	CH3	COOH	C1	[14]
H	CH	2OH	H	D1	[50]	982,3,22β-trihydroxy-24,29-dinor-1,3,5(10),7-friedelatetraene-6,21-dione-23-al	OH	OH	CHO	H	Maytefolins A	H=O	α-OHβ-OH	-	3-oxo-11α	=O-	A2	[18]
CH	3	H	-methoxyolean-12-ene	=OH	H	CH2OH	CH3	B1	H	α-OCH3[44]
CH	3	H	H	CH3	CH3	C1	[24]
114	Krukovines D	=O	OH	CH2OH	H	D1	[50]	4	742,22β-dihydroxyl-3-methoxy-24,29-dinor-1,3,5(10),7-friedelatetraene-6,21-dione	OH	OH	CH3	H	=O	β-OH	-	-	3-oxolup-20(29)-en-30-al	H	H	=OA2	CH3[18]
H	H	H	CH	3	CHO	B1	[45]
99	22α-hydroxy-29-methoxy-3β-tetradecanoate-olean-12-ene	β-COOC13H27	H	H	CH3	α-OH	H	CH3	COOMe	C1	[31]	5	2,3,22β-triihydroxy-23,24,29-trinor-1,3,5(10),7-friedelatetr aene-6,21-dione	OH	OH	H	H	=O	β-OH	-	-	A2	75	30-hydroxylup-20(29)-en-3-one	[	H	H18	=O	CH3	H]
H	H	CH	3	CH	2	OH	B1	[	6
100	45
[
39
]
]
Maytefolin B	-	-	-	-	-	-	-	-	C2	[44]	2,22β-dihydroxyl-3-methoxy-24,29-dinor-1,3,5(10),7-friedelatetraene-6,21-dione	OH	OCH3	CH3	H	=O	76	(11αβ-	OH	-	)-11-hydroxylup-20(29)-en-3-one	H	H-	A2	[	=O	CH318]
H	α	-OH	H	CH	3	CH3	B1	[45]
101	3β-peroxy-7β,25-epoxy-D:B-friedoolean-5-ene	-	-	-	-	-	-	-	-	C3	[48]	7	2,3,22β-trihydroxy-24,29-dinor-1,3,5(10)–friedelatetraene -6,21-dione	OH	CH3	=O	H	H	H	=O	β-OH	77	(3β)-lup-20(30)-ene-3,29-diol	H	H	β-OH	CH3	H	H	H	CH3	CH
102	28-hydroxyolean-12-ene-3,11-dione	=O	H	=O	A3	CH2[18]
OH	H	H	CH	3	CH3	C1	[50]
103	6β,28-dihydroxyolean-12-ene-3,11-dione	=O	β-OH	=O	CH2OH	H	H	CH
115	Krukovines E	=O	H	OH	H	D1	[50]
116	Maytefolins C	-	-	-	-	D2	[44]
117	28-hydroxy-12-ursene-3β-yl-caffeate	β-OCaf	H	CH2OH	H	D1	[52]	2OH	B1	3	CH3	C1	[50]
104
118	3β-stearyloxy-urs-12-ene		H	CH3	H	D1	[56][45]	8
2,15α,22β-trihydroxy-3-methoxy-24,29-dinor-1,3, 5(10)-friedelatriene-21-one	78	11α	OCH3	CH3	H	H	α-OH	H	-hydroxy-epi-betuin	H=O	β-OH	A3	H[18]
α	-OH	CH	3	H	α-OH	H	CH2OH	CH3	B1	[46]	9	3,22β-dihydroxy-24,29-dinor-l(10)-3,5-friedelatriene-2,7,21-trione
79	6β-hydroxybetulin	3-oxo-11	H	H	β-OH	CH3	α-β	-OH	H	H	CH2OH	methoxyolean-12-ene-30-oic acid	=O	H	α-OCH3	CH3	H
119	24-(E)-3-oxo-dammara-20,24-dien-26-al	-	-	-	-	D3	[57]	=O	β-OH	=O	H	-	-	-	-	HA4	[18]
CH	3	B1	COOH	[	CH3	C1	46]
[	51	]
120	24-(Z)-3-oxo-dammara-20,24-dien-26-al	-	-	-	-	D3	[57]	10	3,22β-dihydroxy-24,29-dinor-l(10),3,5–friedelatriene-21-one	H	β-OH	=O	H	-	-	80	24-hydroxybetulin	H	H	=O	105	3-oxo-11α-hydroxyolean-12-ene-30-oic acid	CH2OH	H	H	H	CH2OH	=O	H-	-	A4	CH	α-OH3	CH3[	H18	H]
COOH
121	24-(E)-3-oxo-dammara-20,24-dien-26-ol	CH	B1	H	3	[	46	]
H	CH3	CH2	C1	OH	[	51]	81	Rigidenol-28-aldehyde
D4	[	57	]	11	2,3,22β-trihydroxy-24,29-dinor-25(9→8)-1,3,5(10),7-friedelatetraene-21-one-23-al	β-OH	-	-	-	-	-	-	H	H	=O	CH3	106H	3-oxo-olean-9(11),12-diene-30-oic acid	=O	COOH	-α-OH	H-	A5	CHO	[51]
122	24-(E	CH	3	B1	)-3-oxo-dammara-23-α	-	-[[46]
-	-	18	]
-	-hydroxy-20,24-dien-26-al	H	α-OH	CH3	C4	CHO	D4	[57]	12	23-oxo-iso-tingenone	H	-	-	-	-	-	-	-	A5	[	82	28-hydroxyglochidone	H	CH2OH19]
-	-	-	-	-	-	-	107	3,4-seco-olean-4(23),12-diene-3,29-dioic acid	-	-	-	-B2	-[46]
-	-	-	C5	[	51	]	13	(8S)-7,8-dihydro-7-oxo-tingenoe	=O	83	11α-hydroxy-glochidone	H	=O	H	-	α-OH	CH3	-	-	-	-
108	3α-22	-	-	-	-	β	-	-	-dihydroxyolean-12-en-29-oicacid	B2	[47	αA4	-OH[19]
]
H	H	CH3	β-OH	H	CH3	COOH	C1	[52]	14	(7S, 8S)-7-hydroxy-7,8-dihydro-tingenone	α-OH	H	=O	H	-	-	-	-	A4	84	3-epi-nepeticin	[	H	H	α-OH	CH319]
H	α	-OH	H	CH	3	CH3
109	B1	Olean-9 (11):12-dien-3β-ol	β-OH	[	CH3	-47]
-	-	-	-	-	C4	[53]	15	(8S)-7,8-dihydro-6-oxo-tingenol	OH	CH3	=O	H	H	85	3-epi-	H	calenduladiol	=O	H	H	H
110	3β-Hydroxy-D:B-friedo-olean-5-ene	α	A3	-OH	CH3	H	H	H	OH	-	-CH[19	-3	-	-]
-	-	B1	-	[	47	]	16	23-nor-6-oxo-tingenol	OH	OH	H	H	=O
C6	[	54	]	H	-	-	A2	[19]
86	3α,16β,28-Trihydroxylup-20(29)-ene	H	H	α-OH	CH3	H	H	β-OH	CH2OH	CH3	B1	17	28-hydroxy-friedelane-1,3-dione
111	19α-hydroxy-3-olean-12-en-29-oic acid	=O	[	48	]
H	H	CH3	H	α-OH	CH3	COOH	C1	[55]	=O	H	H	H	CH2OH	CH3	CH3	-	A6	87	3α,16β-dihydroxylup-12-ene	[20]
α	-OH	β-OH	-	-	-	-	-	-	-	B3	[48]	18	Macrocarpin A	OH	CHO	=O	H	H	COOMe	H	H
88	3β,16β	A3	-dihydroxylup-12-ene	[	21	]
β	-OH	β-OH	-	-	-	-	-	-	-	B3	[48]	19	Macrocarpin B	OH	OH	COOH	H	=O	β-OH	-
89	16β-3,4-secolup-20(29)-en-3-oic acid	-	-	--	-	-	-	-A2	-[21]
-	B4	[	48	]	20	Macrocarpin C
90	3-(E)-	OH	OCH3	COOH	H	=O	β-OH	-	-	β	A2	-coumaroylnepeticin	[	H21	H	]
CH	3	H	α	-OH	H	CH3	CH3	B1	[25]	21	Macrocarpin D	α-OH	β-OH	=O	H	-	-	-	-	A4
91	3,4-seco-lupa-4(23):20(29)-diene-3,28-dioicacid 28-methyl ester	-	[	21	]
-	-	-	-	-	-	-	-	B5	[26]	22	Maytenfolone	-	-	-	-	-	-	-	-	A7	[22]
23	6-oxo-iguesterol	-	-	-	-	-
92	1β-Hydroxy-3β-caffeate lup-20(29)-ene	β-OH	H	OCaf	CH3	H	H	H	CH3	CH3	B1	[49]	-	-	-	A8
93	3-oxo-21β-H-hop-22(29)-ene	[	=O	12	]
-	-	-	-	-	-	-	-	B6	[28]	24	6-oxo-tingenol	OH	OH	CH3	H	=O	H	-	-	A2	[12]
25	3-O-methoxy-6-oxo-tingenol	OH	OCH3	CH3	H	=O	H	-	-	A2	[12]
26	Blepharotriol	OH	OH	OH	COOMe	H	H	-	-	A2	[23]
27	6-deoxoblepharodol	OH	CH3	H	H	H	COOMe	H	H	A3	[23]
28	Isoblepharodol	OH	CH3	H	=O	H	COOMe	H	H	A3	[23]
29	7-oxo-blepharodol	OH	64
94	3β-hydroxy-21	CH3	=O	=O	H	COOMe	H	H	A3	[23]
30	15α-hydroxy-tingenone	α-OH	H	H	=O	H	-	-	-	A1	[24]
31	15-dihydro-pristimerin	-	-	-	-	-	-	-	-	A9	[24]
32	Vitideasin	α-COOCH3	H	-	-	-	-	-	-	A10	[24]
33	20β-hydroxy-scutione	α-OH	=O	-	-	-	-	-	-	A10	[24]
34	7-oxo-7,8-dihydro-scutione	-	-	-	-	-	-	-	-	A11	[25]
35	6,23-dioxo-7,8-dihydro-pristimerol-23-oic Acid	OH	COOH	=O	H	H	COOMe	H	H	A3	[25]
36	23-nor-blepharodol	OH	H	=O	H	H	COOMe	H	H	A3	[25]
37	3-methoxy-6-oxo-tingenol-23-oic Acid	OH	OCH3	COOH	H	=O	H	-	-	A2	[25]
38	Retusonine	-	-	-	-	-	-	-	-	A12	[25]
39	21-Oxopristimerine	H	H	COOMe	=O	H	-	-	-	A1	[25]
40	3-O-methyl-6-oxo-pristimerol	OH	OCH3	CH3	COOMe	H	H	-	-	A2	[26]
41	3β,24-epoxy-2α,3α-dihydroxy-D:A-friedooleanan-29-oic acid methyl ester	OH	OH	H	-	-	-	-	-	A13	[27]
42	2α-acetoxy-3β,24-epoxy-3α-hydroxy- D:A-friedooleanan-29-oic acid methyl ester	OAc	OH	H	-	-	-	-	-	A13	[27]
43	3α-hydroxy- D:A-friedooleanan-28-oic acid	α-OH	H	H	COOH	H	-	-	-	A14	[27]
44	3-oxo-D:A-friedooleanan-28,30-olide	-	-	-	-	-	-	-	-	A15	[27]
45	3β,11β-dihydroxyfriedelane	β-OH	β-OH	H	CH3	H	-	-	-	A14	[28]
46	3,4-seco-friedelan-3,11β-olide	-	-	-	-	-	-	-	-	A16	[28]
47	(16β)-16-hydroxy-pristimerin	H	β-OH	COOMe	H	H	-	-	-	A1	[29]
48	12,16-dihydroxyfriedelan-3-one	H	H	α-OH	β-OH	CH3	CH3	CH3	-	A6	[30]
49	3β,24β-epoxy-29-methoxy-2α,3α,6α-trihydroxy-D:A-friedelane	OH	OH	β-OH	-	-	-	-	-	A13	[31]
49a	3β,24β-epoxy-29-methoxy-2α,3α,6α-triacetoxy-D:A-friedelane	OAc	OAc	β-OAc	-	-	-	-	-	A13	[31]
50	Friedel-1-en-3,16-dione	-	-	-	-	-	-	-	-	A17	[32]
51	1α,29-dihydroxyfriedelan-3-one	α-OH	H	H	H	CH3	CH3	CH2OH	-	A6	[32]
52	16β,28,29-trihydroxyfriedelan-3-one	H	H	H	β-OH	CH2OH	CH3	CH2OH	-	A6	[32]
53	Dispemroquinone	=O	H	H	COOMe	-	-	-	-	A5	[33]
54	Scutione	H	=O	-	-	-	-	-	-	A10	[34]
55	Zeylasterone	OH	OH	COOH	COOMe	H	H	-	-	A2	[35]
56	Demethylzeylasterone	OH	OH	COOH	COOH	H	H	-	-	A2	[35]
57	3,15-dioxo-21-hydroxy friedelane	=O	H	=O	CH3	α-OH	-	-	-	A14	[36]
58	Maytenfoliol	H	H	H	H	CH2OH	CH2OH	CH3	-	A6	[37]
β	59	Cangorosin A	H	-	-	-	-	-	-	-	A18	[38]
60	Atropcangorosin A	H(atropisomer of 7-bu)	-	-	-	-	-	-	-	A18	[38]
61	Dihydroatropcangorosin A	6′,7′-dihydro derivative of 8-BU	-	-	-	-	-	-	-	A18	[38]
62	Cangorosin B	-	-	-	-	-	-	-	-	A19	[38]
63	Umbellatin α	α-Me	-	-	-	-	-	-	-	A20	Umbeilatin β	β-Me	-	-	-	-	-	-	-	A20	[39]
65	Tiscutin A	-	-	-	-	-	-	-	-	A21	[40]
66	Triscutin B	-	-	-	-	-	-	-	-	A22	[40]
67	Xuxuarine Eα	-	-	-	-	-	-	-	-	A23	[41]
68	Scutionin αB	-	-	-	-	-	-	-	-	A24	[42]
69	6′,7′-dihydro-scutionin αB	H	-	-	-	-	-	-	-	A25	[42]
70	6′β-methoxy-6′,7′dihydro-scutionin αB	OCH3	-	-	-	-	-	-	-	A25	[42]

2.1.2. Lupane Triterpenes

Lupane triterpenes are characterized by the combination of C-21 and C-19, clustered into a five-membered carbocyclic E ring. There is an isopropyl group substituted at the 19th position of the E ring with an α configuration, as well as a double bond at the C-20(29) position. The rings of the A/B, B/C, C/D and D/E types are all trans. The new triterpenes 3β,28,30-Lup-20(29)-ene triol (71) and 28,30-Dihyroxylup-20(29)-ene-3-one (72) were obtained from M. canariensis [43], while compound maytefolin A (73) was isolated from the leaves of a Brazilian medicinal plant, M. ilicifolia [44]. 3-oxo-lup-20(29)-en-30-al (74), 30-hydroxylup-20(29)-en-3-one (75), (11α)-11-hydroxylup-20(29)-en-3-one (76) and (3β)-lup-20(30)-ene-3,29-diol (77) have been obtained from the hexane extracts of the stems and branches of M. imbricate [45]. Compounds 11α-hydroxy-epi-betuin (78), 6β-hydroxybetulin (79), 24-hydroxybetulin (80), rigidenol-28-aldehyde (81) and 28-hydroxyglochidone (82) have been isolated from M. cuzcoina and M. chiapensis [46]. Compounds 11α-hydroxy-glochidone (83), 3-epi-nepeticin (84) and 3-epi-calenduladiol (85) were separated from the root barks of M. cuzcoina and the leaves of M. chiapensis [47]. Four new triterpenes, including 3α,16β,28-Trihydroxylup-20(29)-ene (86), 3α,16β-dihydroxylup-12-ene (87), 3β,16β-dihydroxylup-12-ene (88) and 16

2.1.4. Other Triterpenes

In addition to the above, other types of triterpene compounds have also been isolated from Maytenus. These include triterpene dimers, ursane triterpenes and dammarane triterpenes. The compound 3-Oxo-methoxyurs-12-ene (112) was isolated from M. spinosa [24]. Three ursane triterpenes, krukovines B, D and E (113–115), were obtained from M. krukovii [50]. Compound maytefolin C (116) has been isolated from the leaves of M. ilicifolia [44], while 28-hydroxy-12-ursene-3β-yl-caffeate (uvaol-3-caffeate) (117) has been isolated from the methanol extracts of the barks of M. laevis [52]. An ursane triterpene 3β-stearyloxy-urs-12-ene (118) was obtained from M. salicifolia [56]. The stem bark exudates of M. macrocarpa yielded ten dammarane triterpenes, namely, 24-(E)-3-oxo-dammara-20,24-dien-26-al (119), 24-(Z)-3-oxo-dammara-20,24-dien-26-al (120), 24-(E)-3-oxo-dammara-20,24-dien-26-ol (121), 24-(E)-3-oxo-dammara-23-α-hydroxy-20,24-dien-26-al (122), 24-(E)-3-oxo-dammara-23-β-hydroxy-20,24-dien-26-al (123), 24-(E)-3-oxo-dammara-6-β-hydroxy-20, 24-dien-26-al (124), 24-(E)-3-oxo-dammara-6-β-hydroxy-20,24-dien-26-ol (125), 23-(Z)-3, 25-dioxo-25-nor-dammara-20,24-diene (126), 24-(E)-3-oxo-23-methylene-dammara-20,24-dien-26-oico (127), 24(Z)-3-oxodammara20(21),24-dien-27-oic acid (128) and octa-nor-13-hydroxydammara-1-en-3,17-dione (129). This was in 1997, and it was the first time that dammrane triterpenes were isolated from Celastraceae ^[57][58][57,58] (Table 4 and Figure 4).

Figure 4. Seven types (D1–D7) of other triterpenes skeletons.

123
24-(
E
)-3-oxo-dammara-23-
β
-hydroxy-20,24-dien-26-al
H
β	-OH	CH	3	CHO	D4	[57]
124	24-(E)-3-oxo-dammara-6-β-hydroxy-20,24-dien-26-al	β-OH	H	CH3	CHO	D4	[57]
125	24-(E)-3-oxo-dammara-6-β-hydroxy-20,24-dien-26-ol	β-OH	H	CH3	CH2OH	D4	[57]
126	23-(Z)-3,25-dioxo-25-nor-dammara-20,24-diene	-	-	-	-	D5	[57]
127	24-(E)-3-oxo-23-methylene-dammara-20,24-dien-26-oico	-	-	-	-	D6	[58]
128	24(Z)-3-oxodammara20(21),24-dien-27-oic acid	H	H	COOH	CH3	D4	[58]
129	Octa-nor-13-hydroxydammara-1-en-3,17-dione	-	-	-	-	D7	[58]

2.2. Sesqiterpenoids

The most widespread and characteristic metabolites isolated from the Celastraceae family are a large group of unusual and highly oxygenated sesquiterpenoids, based on the [5,11-epoxy-5β,10α-eduesman-4(14)-ene] skeleton known as dihydro-β-agarofum. Sesquiterpenes have multiple substitution sites in their structure, and common substituents include -OH, -OAc, -Ofu, -Obz and -Onic, which is due to the diversification of their positions and types. There is a high probability that there are several new compounds from this group that still need to be discovered [59].

Two sesquiterpene polyesters with new polyhydroxy skeletons, 1α,9α-dibenzoyloxy-6β,8α,15-triacetoxy-4β-hydroxy-dihydro-β-agarofurane (130) and 1α,9α-dibenzoyloxy-2α,6β,8α,15-tetracetoxy-4β-hydroxydihydro-β-agrofurane (131), were isolated from the aerial portions of M. canariensis [60]. Compounds 6β,8β-15-triacetoxy-1α,9α-dibenzoyloxy-4β-hydroxy-β-dihydroagarofuran (132), 1α,6β,8β,15-tetraacetoxy-9α-benzoyloxy-4β-hydroxy-β-dihydroagarofuran (133) and (1S,4S,6R,7R,8R,9R)-1,6,15-triacetoxy-8,9-dibenzoyloxy-4β-hydroxy-β-dihydroagarofuran (134) were isolated from the aerial parts of M. macrocarpa [61]. Compounds (1R,2S,4S,5S,6R,7R,9S,10S)-6,15-diacetoxy-1,2,9-tribenzoyloxy-4-hrdroxy-8-oxo-dihydro-β-agarofuran (135) and 9β-cinnamoyloxy-2β,3β-diacetoxy-6β-hydroxy-lα-nicotinoyloxydihidro-β-agarofuran (136) were separated from M. blepharodes [41]. Eight sesquiterpenoids, including 1α-acetoxy-2α,6β,9β-trtifuroyloxy-4β-hydroxy-dihydro-β-agarofuran (137), 1α,2α-diacetoxy-6β,9β-difuroyloxy-4β-hydroxy-dihydro-β-agarofuran (138), 1α-acetoxy-6β,9β-difuroyloxy-2α,4β-dihydroxy-dihydro-β-agarofuran (139), 1α-acetoxy-2α-benzoyloxy-6β,9β-difuroyloxy-4β-dihydro-β-agarofuran (140), 1α-acetoxy-6β,9β-difuroyloxy-2α-propyonyloxy-4β-hydroxy-dihydro-β-agarofuran (141), 1α-acetoxy-6α,9β-difuroyloxy-2α-(2)-methylbutyroyloxy-4β-hydroxy-dihydro-β-agarofuran (142), 1α,2α,15-triacetoxy-6β,9β-difuroyloxy-4β-hydroxy-dihydro-β-agarofuran (143) and 1α,2α,15-triacetoxy-6β,9β-dibenzoyloxy-4β-hydroxy-dihydro-β-agarofuran (144) were obtained from the n-hexane: Et₂O (1:1) extracts of the fruits of M. cuzcoina [59].

The n-hexane/Et₂O (1:1) extracts of the root barks of M. magellanica yielded eight new dihydro-β-agarofuran sesquiterpenes (145–152), and the n-hexane/Et₂O (1:1) extracts of the root barks of M. chubutensis yielded two more new compounds of this family (153–154). Their structures were elucidated as (1R,2R,4S,5R,7S,9S,10R)-2-acetoxy-1-benzoyloxy-9-cinnamoyloxy-4-hydroxy-dihydro-β-agarofuran (145), (1R,2S,3S,5R,7R,9S,10R)-2-acetoxy-9-benzoyloxy-1-cinnamoyloxy-3-nicotinoyloxy-4-hydroxy-dihydro-β-agarofuran (146), (1R,2S,3S,4S,5S,6R,7R,9S,10R)-2,6-diacetoxy-1-benzoyloxy-9-cinnamoyloxy-3-nicotinoyloxy-4-hydroxy-dihydro-β-agarofuran (147), (1R,2S,3S,4S,5S,6R,7R,9S,10R)-2,6-diacetoxy-1,9-dibenzoyloxy-3-nicotinoyloxy-4-hydroxy-dihydro-β-agarofuran (148), (1R,2S,3S,4S,5R,7S,8S,9R,10R)-2,3-diacetoxy-8,9-dibenzoyloxy-1-nicotinoyloxy-4-hydroxy-dihydro-β-agarofuran (149), (1R,2S,4S,5S,6R,7R,8S,9R,10S)-6,8-diacetoxy-1,2,9-tribenzoyloxy-4-hydroxy-dihydro-β-agarofuran (150), (1R,2S,3S,4S,5R,7S,8S,9R,10R)-2,8-diacetoxy-3,9-dibenzoyloxy-1-nicotinoyloxy-4-hydroxy-dihydro-β-agarofuran (151), (1R, 2S,4R,5S,6R,7R,8S,9R,10S)-6,8-diacetoxy-1,9-dibenzoyloxy-2-nicotinoyloxy-dihydro-β-agarofuran (152), 1α,15-diacetoxy-6β,9β-dibenzoyloxy-2α-nicotinoyloxy-dihydro-β-agarofuran (153) and 1α,15-diacetoxy-6β,9β-dibenzoyloxy-2α-nicotinoyloxy-4β-hydroxy-dihydro-β-agarofuran (154) [62]. Compounds (1R,2S,4S,5S,6R,7R,9S,10S)-1,2,6,9,15-pentaacetoxy-4-hydroxy-8-oxo-dihydro-β-agarofuran (155), (1R,2S,4S,5S,6R,7R,9S,10S)-1,2,9,15-taacetoxy-4,6-dihydroxy-8-oxo-dihydro-β-agarofuran (156), (1R,2S,4S,5S,6R,7R,9S,10S)-1,9,15-triacetoxy-2,4,6-trihydroxy-8-oxo-dihydro-β-agarofuran (157), (1R,2S,3S,4S,5S,6R,7R,9S,10S)-1,2,3,6,9,12,15-heptaacetoxy-4-hydroxy-8-oxo-dihydro-β-agarofuran (158) and 1α,2α,3β,6β,8α,9α,12,15-octaacetoxy-4β-hydroxy-dihydro-β-agarofuran (159) were isolated from the leaves of M. chiapensis [63]. In addition, (1S,4S,5S,6R,7R,8S,9R,10R)-8-acetoxy-1,9-dibenzoyloxy-6-nicotynoyloxy-dihydro-β-agarofuran (160) and (1S,4R,5R,6R,7R,8S,9R,10R)-8-acetoxy-1,9-dibenzoyloxy-4-hydroxy-nicotynoyloxy-dihydro-β-agarofuran (161) have been isolated from the roots of M. apurimacensis [49].

Thirteen sesquiterpenes, including (1R,2S,4S,5S,6R,7R,9S,10R)-115-diacetoxy-2,6-dibenzoyloxy-9-(3-furoyloxy)-4-hydroxy-dihydro-β-agarofuran (162), (1R,2S,4S,5S,6R,7R,9S,10R)-1,2,15-triacetoxy-6-benzoyloxy-9-(3-furoyloxy)-4-hydroxy-dihydro-β-agarofuran (163), (1R,2S,4S,5S,6R,7R,9S,10R)-1,15-diacetoxy-6-benzoyloxy-9-(3-furoyloxy)-2,4-dihydroxy-dihydro-β-agarofuran (164), (1R,2S,4S,5S,6R,7R,9S,10R)-1,15-diacetoxy-6,9-dibenzoyloxy-2,4-hydroxy-dihydro-β-agarofuran (165), (1R,2S,4S,5S,6R,7R,9S,10R)-1,2,6,15-tetracetoxy-9-(3-furoyloxy)-4-hydroxy-dihydro-β-agarofuran (166), (1R,2S,4S,5S,6R,7R,9S,10R)-1-Acetoxy-2,6-dibenzoyloxy-9-(3-furoyloxy)-4-hydroxy-dihydro-β-agarofuran (167), (1S,2S,3S,4S,5R,7R,9S,10R)-2,3-diacetoxy-9-benzoyloxy-1-(3-furoyloxy)-4-hydroxy-dihydro-β-agarofuran (168), (1S,2R,4S,5R,7R,9S,10R)-2-acetoxy-9-benzoyloxy-1-(3-furoyloxy)-4-hydroxy-dihydro-β-agarofuran (169), (1S,2R,4S,5R,7R,9S,10R)-2-Acetoxy-1,9-di-(3-furoyloxy)-4-hydroxy-dihydro-β-agarofuran (170), (1S,2R,4S,5R,7R,9S,10R)-2-Acetoxy-9-trans-cynamoiloxy-1-(3-furoyloxy)-4-hydroxy-dihydro-β-agarofuran (171), (1S,4S,5R,7R,9S,10S)-9-Benzoyloxy-1-(3-furoyloxy)-4-hydroxy-dihydro-β-agarofuran (172), (1S,2R,3R,4R,5S,7R,9S,10R)-2,3-diacetoxy-9-benzoyloxy-1-(3-furoyloxy)-dihydro-β-agarofuran (173) and (1S,2R,4R,5S,7R,9S,10R)-2-Acetoxy-9-benzoyloxy-1-(3-furoyloxy)-dihydro-β-agarofuran (174) have been isolated from the hexanee-Et₂O extracts of the fruits of M. jelskii [64]. Nine new β-dihydroagarofurans, 1α2α,9β,15-tetracetoxy-8β-benzoyloxy-β-dihydroagarofuran (175), 1α-benzoyloxy-2α,6β,8α-triacetoxy-9α-methyllbutyroyloxy-β-dihydroagarofuran (176), 1α,6β-diacetoxy-2α,8α,9α-tribenzoyloxy-β-dihydroagarofuran (177), 1α-benzoyloxy-2α,6β,8α,9α-tetraacetoxy-β-dihydroagarofuran (178), 1α,6β,8α-triacetoxy-9α-benzoyloxy-2α-hydroxy-β-dihydroagarofuran (179), (1R,2S,4R,5S,6R,7R,8R,9S,10S)-1,6-diacetoxy-8,9-dibenzoyloxy-2-h ydroxy-β-dihydroagarofuran (180), 1α,6β,15-triacetoxy-8α-methylbutyroyloxy-9α-benzoyloxy-2α-hydroxy-β-dihydroagaro-furan (181), 1α,6β,15-triacetoxy-8α,9α-dibenzoyloxy-2α-hydroxy-β-dihydroagarofuran (182) and 1α,6β,8β,15-tetracetoxy-2α-hydroxy-9α-benzoyloxy-β-dihydroagarofuran (183), were isolated from the leaves of M. spinosa [65]. Five new compounds, chiapens A–E (184–188), were isolated from M. chiapensis [66].

Compounds 1α,6β-diacetoxy-8α-hydroxy-9β-furoyloxy-β-agarofuran (189), 1α-acetoxy-6β,8α-dihydroxy-9β-furoyloxy-β-agarofuran (190), 1α-benzoyloxy-2α,3β,6β,9β,14-pentaacetoxy-8-oxo-β-agarofuan (191) and 1α-furoyloxy-2α,3β,6β,9β,14-pentaacetoxy-8-oxo-β-agarofuan (192) were obtained from an extract of the seeds of M. boaria [67]. Bilocularins A−I (193–201) were isolated from M. bilocularis. In addition, bilocularins D–F are the first examples of dihydro-b-agarofurans, which bear a hydroxyacetate group ^[68][69][68,69]. Compounds (1S,4S,5S,6R,7R,8R,9R,10S)-6-acetoxy-4,9,10-trihydroxy-2,2,5a,9-tetramethyloctahydro-2H-3,9a-methanobenzo[b]oxepin-5-yl furan-3-carboxylate (202), (1S,4S,5S,6R,7R,8R,9R,10S)-6-acetoxy-4,9-dihydroxy-2,2,5a,9-tetramethyloctahydro-2H-3,9a-methanobenzo[b]oxepine-5,10-diyl bis(furan-3-carboxylate) (203), (1S,4S,5S,6R,7R,9S,10S)-6-acetoxy-9-hydroxy-2,2,5a,9-tetramethyloctahydro-2H-3,9a-methanobenzo[b]oxepine-5, 10-diyl bis(furan-3-carboxylate) (204) and (1S,4S,5S,6R,7R,9S, 10S)-6-acetoxy-10-(benzoyloxy)-9-hydroxy-2,2,5a,9-tetramethyloctahydro-2H-3,9a-methanobenzo[b]-oxepin-5-yl furan-3-carboxylate (205) were isolated from the seeds of M. boaria ^[70][71][70,71]. Compounds 2β,6β-diacetoxy-1α,9β-dibenzoyl-3β-hydroxy-dihydro-β-agarofuran (206), 1α,2α,6β,8α-tetraacetoxy-9β-benzoyl-15-hydroxy-dihydro-β-agarofuran (207) and 1α,2α,6β,8α,15-pentaacetoxy-9β-benzoyl-dihydro-β-agarofuran (208) have been separated from M. boaria [72]. 1β-acetoxy-9α-benzoyloxy-2β,6α-dinicotinoyloxy-β-dihydroagarofuran (209) was obtained from the anti-microbially active ethanol extracts of M. heterophylla [73]. In addition, an eudesmane glucoside, boarioside (210), has been isolated from M. boaria [74]. Compounds 4-deacetyl-10-oxo-dihydrobotrydial (211) and 4β-acetoxy-9β,10β,15α-trihydroxyp robotrydial (212) were obtained from solid cultures of an endocytic fungal strain, Phomopsis species Lz42, cultivated on M. hookeri [75] (Table 5 and Figure 5).

Figure 5. Seven types (E1–E7) of sesqiterpenoids skeletons.

Table 5. The sesqiterpenoids isolated from Maytenus.

No.	Name	R1	R2	R3	R4	R5	R6	R7	R8	Type	Ref.
130	1α,9α-dibenzoyloxy-6β,8α,15-triacetoxy-4β-hydroxy-dihydro-β-agarofurane	OBz	H	H	OAc	CH3	α-OAc	α-OBz	CH2OAc	E1	[60]
131	1α,9α-dibenzoyloxy-2α,6β,8α,15-tetracetoxy-4β-hydroxydihydro-β-agrofurane	OBz	α-OAc	H	OAc	CH3	α-OAc	α-OBz	CH2OAc	E1	[60]
132	6β,8β-15-triacetoxy-1α,9α-dibenzoyloxy-4β-hydroxy-β-dihydroagarofuran	OBz	H	H	OAc	CH3	β-OAc	α-OBz	CH2OAc	E1	[61]
133	1α,6β,8β-15-tetraacetoxy-9α-benzoyloxy-4β-hydroxy-β-dihydroagarofuran	OAc	H	H	OAc	CH3	β-OAc	α-OBz	CH2OAc	E1	[61]
134	(1S,4S,6R,7S,8S,9R)-1,6,15- triacetoxy-8,9-dibenzoyloxy-4β-hydroxy-β-dihydroagarofuran	OAc	H	H	OAc	CH3	α-OBz	β-OBz	CH2OAc	E1	[61]
135	(1R,2S,4S,5S,6R,7R,9S,10S)-6,15-diacetoxy-1,2,9-tribenzoyloxy-4-hrdroxy-8-oxo-dihydro-β-agarofuran
-dinicotinoyioxy-
β
-dihydro-agarofuran(heterophylline)
-
-
-
-
-
-
-
-
E4
[
73
]
210
Boarioside
-
-
-
-
-
-
-
-
E5
[
74
]
211
4-deacetyl-10-oxo-dihydrobotrydial
-
-
-
-
-
-	-	-	E6	[	75	]
212	4β-acetoxy-9β,10β,15α-trihydroxyp robotrydial	-	-	-	-	-	-	-	-	E7	[75]

2.3. Alkaloids

2.3.1. Sesquiterpene Pyridine Alkaloids

Among the naturally occurring nitrogen containing compounds, the pyridine alkaloids constitute an important group, and these are relatively rare natural products. The Celastraceae family is a rich source of sesquiterpene pyridine alkaloids. These compounds are endowed with a novel type of chemical diversity, and have complicated stereo-chemistries. They also possess a broad spectrum of biological activities, such as having immunosuppressive and anti-tumor properties. The vast majority of macrolide sesquiterpene pyridine alkaloids, from the genus Maytenus, are based on the [5,11-epoxy-5β,10a-eduesman-4(14)-ene] skeleton known as dihydro-β-agarofum. These compounds are characterized by a pyridine dicarboxylic acid macrocyclic bridge (such as evoninic, wilfordic and hydroxywilfordic acids), linked via two ester moieties at the C-3 and C-15 positions ^[65][76][65,76]. Many of these alkaloids have been isolated by organic chemists over recent years. Below we summarize their information, including the names of compounds, their original plant source as well as their structures.

The potent anti-feedant wilforine (213) was isolated from M. rigida [77]. Compounds emarginatines A–H (214–221) and emarginatinine (222) were obtained from M. emarginata and the leaves of M. diversifolia. ^{[11][22][78][79]}[11,22,78,79]. Ebenifoline W-I (223), ebenifoline E-I (224) and ebenifoline E-II (225) were separated from the stem bark methanol extracts of M. ebenifolia Reiss [80]. Compounds aquifoliunines E-I-IV (226–229) have been obtained from the root barks of M. aquiJolium. ^[81][82][81,82], while ilicifoliunines A–B (230–231) and mayteine (232) were isolated from the root barks of M. ilicifolia [83]. Laevisines A (233) and B (234) have been separated from the CHCl₃:MeOH (9:1) extracts of the barks of M. laevis [84]. Compounds mekongensine (235), 7-epi-mekongensine (236), 1-O-benzoyl-1-deacetylmekongensine (237), 9′-deacetoxymekongensine (238), 1-O-benzoyl-1-deacetyl-9′-deacetoxymekongensine (239), 7-epi-euojaponine A (240), 2-O-benzoyl-2-deacetylmayteine (241) and 7-epi-5-O-benzoyl-5-deacetylperitassine A (242) have been isolated from the roots of M. mekongensis [85]. The compound 5-benzoyl-5-deacetylwilforidine (243) was isolated from M. buchananii (Loes.) R. Wilczek. This appears to be the first sesquiterpene nicotinoyl alkaloid found which was based on hydroxywilfordic acid, with a benzoyl group at C-5 position [86]. Compounds putterines A (244) and B (245) have been separated from the roots of M. putterlickoides [76]. The compound 7-(acetyloxy)-O¹¹-benzoyl-O^2,11-deacetyl-7-deoxoevonine (246) was isolated from the methanol extracts of the barks of the Colombian medicinal plant, M. laevis [52]. Chiapenines ES-I (247), ES-II (248), ES-III (249) and ES-IV (250) were isolated from the leaves of M. chiapensis [87]. Compound jelskiine (251) was obtained from M. jelskii and M. cuzcoina [88]. Compounds O⁹-benzoyl-O⁹-deacetylevonine (252) and 8β-acetoxy-O¹-benzoyl- O¹-deacetyl-8-deoxoevonine (253) have been separated from the organic extracts of the roots of M. spinosa [24]. Compounds 1α,2α,6β,8β,9α,15-hexacetoxy-4β-hydroxy-3β,13-[2′-(3-carboxybutyl)] nicotinicacid-dicarbo-lactone-β-dihydroagarofuran (254), 1α,2α,9α,15-tetracetoxy-4β,6β-dihydroxy-8-oxo,3β,13-[4′-(3-carboxybutyl)]nicotinicacid-dicarbolactone-β-dihydroagarofuran (255), 1α,2α,9α,15-tetracetoxy-4β,6β,8β-trihydroxy-3β,13-[4′-(3-carboxybutyl)] nicotinicacid-dicarbolactone-β-dihydroagarofuran (256) and 1α,2α,8β,9α,15-pent acetoxy-4β,6β-dihydroxy-3β,13-[4′-(3-carboxybutyl)] nicotinicaciddicarbolactne-β-dihydroagarofuran (257) were isolated from the leaves of M. spinosa [65]. Compounds 4-deoxyalatamine (258), 1-O-benzoyl-1-deacetyl-4-deoxy-alatamine (259), 1,2-O-dibenzoyl-1,2-deacetyl-4-deoxyalatamine (260) and 4-deoxyisowilfordine (261) were obtained from an ethyl acetate extract of M. oblongata stems [31] (Table 6 and Figure 6).

Figure 6. Fifteen types (F1–F15) of sesquiterpene pyridine alkaloids skeletons.

Table 6. The sesquiterpene pyridine alkaloids isolated from Maytenus.

No.	Name	R1	R2	R3	R4	R5	Type	Ref.
213	Wilforine	-	-	-	-	-	F1	[77]
214	Emarginatine-A	OAc	OAc	OAc	H	OAc	F2	[78]
215	Emarginatine-B	OAc	Benzoate	H	OAc	OAc	F2	[78]
216	Emarginatine-C	OAc	OH	OAc	H	OAc	F2	[79]
217	Emarginatine-D	OA	OAc	OAc	H	OAc	F2	[79]	OBz	α-OBz	H	OAc	CH3	O
218	α	-OBz	Emarginatine-E	CH	2	OAc	E1	[41]
OH	OH	H	OAc	OAc	F2	[79]	136	9β-cinnamoyloxy-2β,3β-diacetoxy-6β-hydroxy-lα-nicotinoyloxydihidro-β-agarofuran	ONic	β-OAc
219	Emarginatine-F		OAcβ-OAc	OH	CH3	H	OHH	β-OCin	CH3	E1	[41]
OAc	F2	[	11	]	137	1α-acetoxy-2α,6β,9β-trtifuroyloxy-4β-hydroxy-dihydro-β- agarofuran	OAc	α-OFu	H	OFu	CH3	H	β-OFu	CH3	E1
220	Emarginatine-G	CH3CH=CCH3OO	[	59	OAc	OAc	H]
OAc	F2	[	11	]	138	1α,2α-diacetoxy-6β,9β-difuroyloxy-4β-hydroxy-dihydro-β- agarofuran	OAc	α-OAc	H	OFu	CH3	H	β-OFu	CH3	E1	[59]
221	Emarginatine-H	OAc	OAc	OAc	H	OH	F2	[22]	139	1α-acetoxy-6β,9β-difuroyloxy-2α,4β-dihydroxy-dihydro-β-agarofuran	OAc	α-OH	H	OFu	CH3	H	β-OFu
222	Emarginatinine	-	-	-	-	-	F3CH3	E1	[59]
[	79	]	140	1α-acetoxy-2α-benzoyloxy-6β,9β-difuroyloxy-4β-dihydro-β-agarofuran	OAc	α-OBz	H	OFu	CH3
223	H	β	-OFu	CH	3	E1	Ebenifoline W-I	[59]
β	-OAc	OBz	OBz	OAc	-	F4	[80]	141	1α-acetoxy-6β,9β-difuroyloxy-2α-propyonyloxy-4β-hydroxy-dihydro-β-agarofuran	OAc	α-OPr	H	OFu	CH3	H	β-OFu	CH3	E1
224	Ebenifoline E-I	β-OAc	OAc	[	OH	59	OBz	OAc	F5]
[	80	]	142	1α-acetoxy-6α,9β-difuroyloxy-2α-(2)-methylbutyroyloxy-4β-hydroxy-dihydro-β-agarofuran	OAc	α-OButMe	H
225	OFu	Ebenifoline E-II	β-OAc	OBz	OAcCH3	H	OBzβ-OFu	OAcCH3	E1	F5[59]
[	80	]	143	1α, 2α,15-triacetoxy-6β,9β-difuroyloxy-4β- hydroxy-dihydro-β-agarofuran	OAc	α-OAc	H
226	Aquifoliunine E-I	αOFu	-OBzCH3	OAc	OAc	OAcH	CH2β-OFu	OAc	F5CH2OAc	E1	[59]
[	81	]	144	1α, 2α,15-triacetoxy-6β,9β-dibenzoyloxy-4β- hydroxy-dihydro-β-agarofuran	OAc	α-OAc	H	OBz	CH3	H	β
227	-OBz	Aquifoliunine E-II	α-OH	OAc	OHCH	OAc	CH2OAc2OAc	E1	[59]
F5	[	81	]	145	(1R,2R,4S,5R,7S,9S,10R)-2-acetoxy-1-benzoyloxy-9-cinnamoyloxy-4-hydroxy- dihydro-β-agarofuran	OBz	β-OAc	H	H	CH3	H	β-OH	CH
228	3	E1	Aquifoliunine E-III	[	62	]
α	-OH	OAc	OAc	OAc	CH2OAc	F5	[82]	146	(1R,2S,3S,5R,7R
229	,9S,10R)-2-acetoxy-9-benzoyloxy-1-cinnamoyloxy-3-nicotinoyloxy-4-hydroxy-dihydro-β-agarofuran	OCin	Aquifoliunine E-IV	β-OAc	αβ-ONic	H	-ONicCH3	H	H	OAc	OAcCH3	E1	OAc[62]
CH	2	OAc	F5	[	82]	147	(1R,2S,3S,4S,5S,6R,7R,9S,10R)-2,6-diacetoxy-1-benzoyloxy-9-cinnamoyloxy-3-nicotinoyloxy-4-hydroxy-dihydro-
230	β-agarofuran	OBz	β-OAc	β-ONic	OAc	Ilicifoliunines A	α-OBz	OH	OAc	OAcCH3	CHH	2β-OCin	CH3	E1	OAc[62]
F5	[	83	]	148	(1R,2S,3S,4S,5S,6R,7R,9S,10R)-2,6-diacetoxy-1,9-dibenzoyloxy-3-nicotinoyloxy-4-hydroxy-dihydro-β-agarofuran	OBz	β-OAc	β-ONic	H	CH3	H	β-OBz	CH3	E1	[62]
149	(1R,2S,3S,4S,5
231	Ilicifoliunines B	α-OBz	OAc	OAc	CH2OAc	-	F4	[83]	R,7S,8S,9R,10R)-2,3-diacetoxy-8,9-dibenzoyloxy-1-nicotinoyloxy-4-hydroxy-dihydro-β-agarofuran	ONic	β-OAc	β-OAc	H	CH
232	3	Mayteine	β-OAc	OAc	OAcβ	OBz	CH2OAc-OBz	β-OBz	CH	F5	[83]3	E1	[62]
150	(1R,2S,4S,5S,6R,7R,8S,9R,10S)-6,8-diacetoxy-1,2,9-tribenzoyloxy-4-hydroxy-dihydro-β-agarofuran	OBz	α
233	-OBz	H	Laevisines A	OAc	β-OAc	OAc	OAc	OCOC(CH3)=CHCH3CH3	β-OAc	β-OBz	CH3	E1	[62]
CH	2	OAc	F5	[	84]	151	(1R,2S,3S,4S,5R,7S,8S,9R,10R)-2,8-diacetoxy-3,9-dibenzoyloxy-1-nicotinoyloxy-4-hydroxy-dihydro-β-agarofuran	ONic	β-OAc	β
234	Laevisines B	β-OAc-OBz	H	β-OAc	β-OBz	CH3	-	E2	[62]
OAc	ONic	CH2OAc	-	F4	[84]	152	(1R
235	,2S,4R,5S,6R,7R,8S,9R,10S)-6,8-diacetoxy-1,9-dibenzoyloxy-2-nicotinoyloxy-dihydro-β-agarofuran	OBz	Mekongensine	α-ONic	H	OAc	β-OAc	β-OBz	CH3	-	E2	Ac[62]
H	OAc	OAc	-	F6	[85]	153	1α,15-diacetoxy-6β,9β-dibenzoyloxy-2α-nicotinoyloxy-dihydro-β-agarofuran	OAc	α-ONic	H	OBz	H	β-OBz	CH3	-	E2	[62]
154	1α,15-diacetoxy-6β,9β-dibenzoyloxy-2α
236	7-epi-mekongensine	Ac	OAc	H	OAc	-	F6	[85]	-nicotinoyloxy-4β-hydroxy-dihydro-β-agarofuran	OAc	α-ONic	H	OBz	CH3	H
237	β	-OBz	CH	2	OAc	E1	1-O-benzoyl-1-deacetylmekongensine	[	Bz62]
H	OAc	OAc	-	F6	[85]	155	(1R,2S,4S,5S,6R,7R,9S,10S)-1,2,6,9,15-pentaacetoxy-4-hydroxy-8-oxo-dihydro-β-agarofuran	OAc	α-OAc	H	OAc	CH3	O	α-OAc	CH2OAc	E1	[63]
238	9′-deacetoxymekongensine	Ac	H	OAc	H	-	F6	[85]	156	(1R,2S,4S,5S,6R,7R,9S,10S)-1,2,9,15-taacetoxy-4,6-dihydroxy-8-oxo-dihydro-β-agarofuran
239	1-	OAc	O-benzoyl-1-deacetyl-9′-deacetoxymekongensine	Bzα-OAc	H	OH	CH3	O	H	OAcα	H	-	F6-OAc	[85]CH2OAc	E1	[63]
157	(1R,2S,4S,5S,6R,7R,9S,10S)-1,9,15-triacetoxy-2,4,6-trihydroxy-8-oxo-dihydro-β-agarofuran	OAc	α-OH	H	OH	CH3	O	α-OAc	CH2OAc	E1	[63]
240	7-epi-euojaponine	Bz	Ac	H	OAc	H	F7	[85]	158	(1R,2S,3S,4S,5S,6R,7R,9S,10S)-1,2,3,6,9,12,15-heptaacetoxy-4-hydroxy-8-oxo-dihydro-β-agarofuran	OAc
241	2-O-benzoyl-2-deacetylmayteine	Bzα-OAc	β-OAc	OAc	CH	Bz2OAc	O	α-OAc	CH2OAc	E1	Ac	H	OAc	F7	[85[63]
]	159	1α,2α,3β,6β,8α,9α,12,15-octaacetoxy-4β-hydroxy-dihydro-β-agarofuran
242	7-epi-5-	OAc	Oα	-OAc	β-OAc	OAc	-benzoyl-5-deacetylperitassine A	CH2OAc	α-OAc	α-OAc	CH2OAc	E1	[63]
-	-	-	-	-	F8	[85]	160	(1S,4S,5S,6R,7R,8S,9R,10R)-8-acetoxy-1,9-dibenzoyloxy-6-nicotynoyloxy-dihydro-β-agarofuran	OBz	H	H	ONic	α-OAc	α-OBz	CH3	-	E2	[49]
161	(1S,4R,5R,6R,7R,8S,9R,10R)-8-acetoxy-1,9-dibenzoyloxy-4-hydroxy-nicotynoyloxy-dihydro-β-agarofuran	OBz	H	H	ONic	CH3	α-OAc	α-OBz	CH3	E1	[49]
162	(1
243	5-benzoyl-5-deacetylwilforidine	-	-	-	-	-	F9	[86]
244	Putterines A		OAc	COOCH3	COOCH3	CH2OAc	F5	[76]	R,2S,4S,5S,6R,7R,9S,10R)-1,15-diacetoxy-2,6-dibenzoyloxy-9-(3-furoyloxy)-4-hydroxy-dihydro-β-agarofuran	OAc	α-OBz	H	OBz	CH3	H	α-OFu
245	Putterines B	CH		2	OAc	E1	OAc	COOCH(CH3)2[64	COOCH3	CH2OAc	F5]
[	76	]	163	(1R,2S,4S,5S,6R,7R,9S,10R)-1,2,15-triacetoxy-6-benzoyloxy-9-(3-furoyloxy)-4-hydroxy-dihydro-β-agarofuran	OAc	α-OAc
246	7-(acetyloxy)-O11-benzoyl-O2,11-deacetyl-7-deoxoevonine	H	OBz	CH3	H	α-OFu	CH2OAc	E1	[64]
β	-OAc	OAc	OH	OAc	CH2OBz	F5	[52]	164	(1R,2S,4S,5S,6R,7R,9S,10R)-1,15-diacetoxy-6-benzoyloxy-9-(3-furoyloxy)-2,4-dihydroxy-dihydro-β-agarofuran	OAc	α-OH	H	OBz	CH3	H	α
247	-OFu	Chiapenines ES-I	OBz	OBzCH	α-OAc	-2OAc	-	F10	[87E1	[64]
]	165	(1R,2S,4S,5S,6R,7R,9S,10R)-1,15-diacetoxy-6,9-dibenzoyloxy-2,4-hydroxy-dihydro-β-agarofuran	OAc	α-OH	H	OBz	CH3	H	α-OBz	CH2OAc	E1	[64]
248	Chiapenines ES-II	OBz	OBz	=O	-	-	F10	[87]	166	(1R,2S,4S,5S,6R,7R,9S,10R)-1,2,6,15-tetracetoxy-9-(3-furoyloxy)-4-hydroxy-dihydro-β-agarofuran	OAc	α-OAc	H	OAc	CH3	H	α-OFu
249	Chiapenines ES-III	OBz	CH	2	OAc	OHE1	[	=O64]
-	-	F10	[	87]	167	(1R,2S,4S,5S,6R,7R,9S,10R)-1-Acetoxy-2,6-dibenzoyloxy-9-(3-furoyloxy)-4-hydroxy-dihydro-β-agarofuran	OAc	α-OBz	H	OBz	CH3	H	α-OFu	CH3	E1	[64
250	Chiapenines ES-IV	OAc	OH	]
=O	-	-	F10	[87]	168	(1S,2S,3S,4S,5R,7R,9S,10R)-2,3-diacetoxy-9-benzoyloxy-1-(3-furoyloxy)-4-hydroxy-dihydro-β-agarofuran	OFu	β-OAc	β-OAc	H	CH3	H	α-OBz	CH3	E1	[64]
251	Jelskiine	OiBut	α-OAc	OH	OAc	-	F11	[88]	169	(1S,2R,4S,5R,7R,9S,10R)-2-acetoxy-9-benzoyloxy-1-(3-furoyloxy)-4-hydroxy-dihydro-β-agarofuran
252	O9-benzoyl-	OFu	Oβ	-OAc	9-deacetylevonine	OBz	=OH	H	CH3	H	α-OBz	OAc	OAc	-	F11	[24CH3	E1	][64]
170	(1S,2R,4S
253	,5R,7R,9S,10R)-2-Acetoxy-1,9-di-(3-furoyloxy)-4-hydroxy-dihydro-β-agarofuran	8β-acetoxy-O	OFu	1	β-OAc	H	H	CH3	H	α-OFu	CH3	E1	-benzoyl- O	[64]
1	-deacetyl-8-deoxoevonine	OAc	β-OAc	OAc	OBz	-	F11	[24]	171	(1S,2R,4S,5R,7R,9S,10R)-2-Acetoxy-9-trans-cynamoiloxy-1-(3-furoyloxy)-4-hydroxy-dihydro-β-agarofuran	OFu	β-OAc	H	H
254	1α,2α	CH	3	H	,6β,8β,9α,15-hexacetoxy-4β-hydroxy-3β,13-[2′-(3-carboxybutyl)]nicotinicacid-dicarbo-lactone-β-dihydroagarofuran	-α-OCin	-	-	-	-	F12	[65CH3	E1	][64]
172	(1S,4S,5R,7R,9S,10S)-9-Benzoyloxy-1-(3-furoyloxy)-4-hydroxy-dihydro-β-agarofuran	OFu	H	H	H	CH3	H
255	1α,2α,9α,15-tetracetoxy-4	α	-OBz	CH	3	E1	β,6	[64]
β	-dihydroxy-8-oxo,3β,13-[4′-(3-carboxybutyl)]nicotinicacid-dicarbolactone-β-dihydroagarofuran	=O	-	-	-	-	F13	[65]	173
256	(1S,2	1αR,3R,4R,5,2α,9α,15-tetracetoxy-4βS,7R,9S,10,6β,8β-trihydroxy-3βR)-2,3-diacetoxy-9-benzoyloxy-1-(3-furoyloxy)-dihydro-β-agarofuran	,13-[4′-(3-carboxybutyl)]nicotinicacid-dicarbolactone-	OFu	ββ	-OAc	β-OAc	H	-dihydroagarofuran	β-OH	-H	α-OBz	CH	-	-	-3	-	E2	F13	[65][64]
174	(1S,2R,4R,5S,7R,9S,10R)-2-Acetoxy-9-benzoyloxy-1-(3-furoyloxy)-dihydro-β-agarofuran
257	1α,2α	OFu	,8β,9α,15-pent acetoxy-4β,6β-dihydroxy-3ββ	-OAc	H	,13-[4′-(3-carboxybutyl)]nicotinicaciddicarbolactne-	H	β	H	-dihydroagarofuran	α-OBz	CH3	-	E2	[64]
β	-OAc	-	-	-	-	F13	[65]	175	1α,2α,9β,15-tetracetoxy-8β-benzoyloxy-β-dihydroagarofuran	OAc	α-OAc	H	H	β-OBz	α-OAc	CH2OAc	-	E2	[65]
258	4-deoxyalatamine	OAc	OAc	-	-	-	F14	[31]	176	1α-benzoyloxy-2α,6β,8α-triacetoxy-9α-methyllbutyroyloxy-β-dihydroagarofuran	OBz	α-OAc	H	OAc	α-OAc	α-OMeBut	CH3
259	1-O-benzoyl-1-deacetyl-4-deoxy-alatamine	OBz	OAc	-	E2	[	-	-	-65]
F14	[	31	]	177	1α,6β-diacetoxy-2α,8α,9α-tribenzoyloxy-β-dihydroagarofuran	OAc	α-OBz	H	OAc	α-OBz	α-OBz	CH3	-	E2	[65]
260	1,2-O-dibenzoyl-1,2-deacetyl-4-deoxyalatamine	OBz	OBz	-	-	-	F14	[31]	178	1α-benzoyloxy-2α,6β,8α,9α-tetraacetoxy-β-dihydroagarofuran	OBz	α-OAc	H	OAc	α-OAc	α-OAc	CH3	-	E2	[65]
261	4-deoxyisowilfordine	-	-	-	-	-	F15	[31]	179	1α,6β,8α-triacetoxy-9α-benzoyloxy-2α-hydroxy-β-dihydroagarofuran	OAc	α-OH	H	OAc	α-OAc	α-OBz	CH3	-	E2	[65]
180	(1R,2S,4R,5S,6R,7R,8R,9S,10S)-1,6-diacetoxy-8,9-dibenzoyloxy-2-h ydroxy-β-d ihydroagarofuran	OAc	α-OH	H	OAc	α-OBz	α-OBz	CH3	-	E2	[65]
181	1α,6β,15-triacetoxy-8α-methylbutyroyloxy-9α-benzoyloxy-2α-hydroxy-β-dihydroagaro-furan	OAc	α-OH	H	OAc	α-OMeBut	α-OBz	CH2OAc	-	E2	[65]
182	1α,6β,15-triacetoxy-8α,9α-dibenzoyloxy-2α-hydroxy-β-dihydroagarofuran	OAc	α-OH	H	OAc	α-OBz	α-OBz	CH2OAc	-	E2	[65]
183	1α,6β,8β,15-tetracetoxy-2α-hydroxy-9α-benzoyloxy-β-dihydroagarofuran	OAc	α-OH	H	OAc	β-OAc	α-OBz	CH2OAc	-	E2	[65]
184	Chiapens A	OH	α-OAc	H	OAc	α-OBz	α-OBz	CH2OAc	-	E2	[66]
185	Chiapens B	OAc	α-OAc	H	OAc	α-OBz	α-OBz	CH2OAc	-	E2	[66]
186	Chiapens C	OH	H	H	OAc	α-OBz	α-OBz	CH2OAc	-	E2	[66]
187	Chiapens D	OAc	α-OAc	H	OBut	H	α-OBz	CH2OAc	-	E2	[66]
188	Chiapens E	OAc	α-OAc	β-OAc	OAc	O	α-OBz	CH2OAc	-	E2	[66]
189	1α,6β-diacetoxy-8α-hydroxy-9β-furoyloxy-β-agarofuran	OAc	H	H	OAc	α-OH	β-OFu	CH3	-	E2	[67]
190	1α-acetoxy-6β,8α-dihydroxy-9β-furoyloxy-β-agarofuran	OAc	H	H	OH	α-OH	β-OFu	CH3	-	E2	[67]
191	1α-benzoyloxy-2α,3β,6β,9β,14-pentaacetoxy-8-oxo-β-agarofuan	OBz	α-OAc	β-OAc	OBz	O	OAc	CH2OAc	-	E2	[67]
192	1α-furoyloxy-2α,3β,6β,9β,14-pentaacetoxy-8-oxo-β-agarofuan	OFu	α-OAc	β-OAc	OFu	O	OAc	CH2OAc	-	E2	[67]
193	Bilocularins A	OAc	H	H	OAc	α-OH	α-OBz	CH2OAc	-	E2	[68]
194	Bilocularins B	OAc	H	H	OH	α-OAc	α-OBz	CH2OAc	-	E2	[68]
195	Bilocularins C	OAc	H	H	OAc	O	α-OBz	CH2OAc	-	E2	[68]
196	Bilocularins D	OHAc	α-OAc	H	OAc	CH3	H	β-OtCin	CH2OBz	E1	[69]
197	Bilocularins E	OHAc	α-OAc	H	OAc	CH3	H	β-OtCin	CH2OtCin	E1	[69]
198	Bilocularins F	OHAc	α-OAc	H	OAc	CH3	H	β-OtCin	CH2OH	E1	[69]
199	Bilocularins G	OAc	α-OAc	H	OAc	CH3	H	β-OtCin	CH2OAc	E1	[69]
200	Bilocularins H	OAc	α-OH	H	OAc	CH3	H	β-OtCin	CH2OH	E1	[69]
201	Bilocularins I	OAc	α-OH	H	ONic	CH3	H	β-OtCin	CH3	E1	[69]
202	(1S,4S,5S,6R,7R,8R,9R,10S)-6-acetoxy-4,9,10-trihydroxy-2,2,5a,9-tetramethyloctahydro-2H-3,9a-methanobenzo[b]-oxepin-5-yl furan-3-carboxylate	OAc	H	H	OH	CH3	α-OH	β-OFu	CH3	E1	[70]
203	(1S,4S,5S,6R,7R,8R,9R,10S)-6-acetoxy-4,9-dihydroxy-2,2,5a,9-tetramethyloctahydro-2H-3,9a-methanobenzo[b]oxepine-5,10-diylbis(furan-3-carboxylate)	OAc	H	H	OFu	CH3	α-OH	β-OFu	CH3	E1	[71]
204	(1S,4S,5S,6R,7R,9S,10S)-6-acetoxy-9-hydroxy-2,2,5a,9-tetramethyloctahydro-2H-3,9a-methanobenzo[b]oxepine-5,10-diyl bis(furan-3-carboxylate)	OAc	H	H	OFu	CH3	H	β-OFu	CH3	E1	[71]
205	(1S,4S,5S,6R,7R,9S,10S)-6-acetoxy-10-(benzoyloxy)-9-hydroxy-2,2,5a,9-tetramethyloctahydro-2H-3,9a-methanobenzo[b]-oxepin-5-yl furan-3-carboxylate	OAc	H	H	OBz	CH3	H	β-OFu	CH3	E1	[71]
206	2β,6β-diacetoxy-1α,9β-dibenzoyl-3β-hydroxy-dihydro-β-agarofuran	α-OBz	β-OAc	β-OH	H	β-CH3	-	-	-	E3	[72]
207	1α,2α,6β,8α-tetraacetoxy-9β-benzoyl-15-hydroxy-dihydro-β-agarofuran	α-OAc	α-OAc	H	α-OAc	α-CH2OH	-	-	-	E3	[72]
208	1α,2α,6β,8α,15-pentaacetoxy-9β-benzoyl-dihydro-β-agarofuran	α-OAc	α-OAc	H	α-OAc	α-CH2OAc	-	-	-	E3	[72]
209	1β-acetoxy-9α-benzoyloxy-2β,6α

2.3.2. Maytansinoids

In 1972, Kupchan et al. [7] found a macrolide alkaloid, maytansine (262), which was a natural product that had anti-tumor activities, and this was first isolated from M. serrata. Compound 262 is an anti-tumor agent with a novel structure, and, therefore, is of great clinical interest. Subsequently, maytansine (262), maytanprine (263) and maytanbutine (264) were isolated from M. buchananii [89]. Larson et al. [90] also isolated two new maytansinoid compounds, 2′-N-demethylmaytanbutine (265) and maytanbicyclinol (266) from M. buchananii (Figure 7).

Figure 7. The chemical structures of maytansinoids, isolated from Maytenus.