Friedelane triterpenoids are important characteristic components of the Celastraceae family. Moreover, they are endowed with novel chemical diversity and possess a broad spectrum of biological activities. The friedelane triterpenoids are pentacyclic triterpenes composed of 30 carbons, which are converted from oleanolic acid by methyl shifts. In the five six-membered rings, the A/B, B/C and C/D rings are all trans and the D/E rings are mostly cis (i.e., H-18β). There is one β-CH3 substitution at each of the C-4, C-5, C-9, C-14 and C-17 positions. The C-3 position is often substituted with a hydroxyl group, although sometimes the hydroxyl group is oxidized to a carbonyl group.
The compound pristimerin (
1) was isolated from
M. chuchuhuasca [16]. A new nortriterpene quinone methide, 15
α-hydroxy-21-keto-pristimerine (
2), has been obtained from the root bark of
M. catingarum [17]. Fourteen compounds, including 2,3,22
β-trihydroxy-24,29-dinor-1,3,5(10), 7-friedelatetraene-6,21-dione-23-al (
3), 2,22
β-dihydroxyl-3-methoxy-24,29-dinor-1,3,5(10), 7-friedelatetraene-6,21-dione (
4), 2,3,22
β-triihydroxy-23,24,29-trinor-1,3,5(10), 7-friedelatetr aene-6,21-dione (
5), 2,22
β-dihydroxyl-3-methoxy-24,29-dinor-1,3,5(10), 7-friedelatetraene-6,21-dione (
6), 2,3,22
β-trihydroxy-24,29-dinor-1,3,5(10)-friedelatetraene-6,21-dione (
7), 2,15
α,22
β-trihydroxy-3-methoxy-24,29-dinor-1,3,5(10)-friedelatriene-21-one (
8), 3,22
β-dihydroxy-24,29-dinor-l(10)-3,5-friedelatriene-2,7,21-trione (
9), 3,22
β-dihydroxy-24,29-dinor-l(10), 3,5-friedelatriene-21-one (
10), 2,3,22
β-trihydroxy-24,29-dinor-25(9→8)-1,3,5(10), 7-friedelatetraene-21-one-23-al (
11), 23-oxo-iso-tingenone (
12), (8
S)-7,8-dihydro-7-oxo-tingenoe (
13), (7
S,8
S)-7-hydroxy-7,8-dihydro-tingenone (
14), (8
S)-7,8-dihydro-6-oxo-tingenol (
15) and 23-nor-6-oxo-tingenol (
16) were isolated from the roots of
M. amazonica [18][19]. Compounds 28-hydroxy-friedelane-1,3-dione (
17) and macrocarpins A–D (
18–
21) were obtained from the roots of
M. macrocarpa [20][21], while maytenfolone (
22) has been isolated from
M. diversifolia [22]. Three compounds 6-oxo-iguesterol (
23), 6-oxo-tingenol (
24) and 3-
O-methoxy-6-oxo-tingenol (
25) have been obtained from the root bark of
M. canariensis [12]. Four new triterpenes blepharotriol (
26), 6-deoxoblepharodol (
27), isoblepharodol (
28) and 7-oxo-blepharodol (
29) were separated from
M. blepharodes [23].
Compounds 15α-hydroxy-tingenone (
30), 15-dehydro-pristimerin (
31), vitideasin (
32) and 20
β-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/Et
2O 1:1 extract of the root bark of
M. chubutensis [26]. Compounds 3
β,24-epoxy-2
α,3
α-dihydroxy-D:A-friedooleanan-29-oic acid methyl ester (
41), 2
α-acetoxy-3
β,24-epoxy-3
α-hydroxy-D:A-friedooleanan-29-oic acid methyl ester (
42), 3
α-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 3
β,11
β-dihydroxyfriedelane (
45) and 3,4-seco-friedelan-3,11
β-olide (
46) have been obtained from the hexane extracts of the leaves of
M. robusta [28], while (16
β)-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 3
β,24
β-epoxy-29-methoxy-2
α,3
α,6
α-trihydroxy-D:A-friedelane (
49) and 3
β,24
β-epoxy-29-methoxy-2
α,3
α,6
α-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), 1
α,29-dihydroxyfriedelan-3-one (
51) and 16
β,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-21
α-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 E
α (
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] (
Table 1 and
Figure 1).