1. Introduction
In the last few decades, fungi have attracted tremendous scientific attention due to their capability to biosynthesize diverse classes of bio-metabolites, with varied bioactivities that are utilized for pharmaceutical, medicinal, and agricultural applications
[1][2][3][4][5][6][7][8][9][10][11][12][13][14]. Obviously, the number of reported biometabolites from a fungal origin is rapidly growing
[15][16][17][18][19]. Fungi can produce a wide variety of structurally unique polyketide-derived metabolites; among them are phenalenones, in which various post-modifications, including prenylation, transamination, rearrangement, and oxidation diversify their structures
[20][21][22]. Phenalenones belong to the aromatic ketones, consisting of a hydroxyl-perinaphthenone three-fused-ring system that has been reported as from both microbial and plant sources
[21]. They are recognized as the higher plants’ phytoalexins, which confer resistance toward pathogens
[23][24]. Phenalenones are also known as pollutants, resulting from the combustion of fossil fuels
[21]. The first report of the isolation of a phenalenone derivative from a fungal source was in 1955
[25][26]. Fungal phenalenones have immense structural diversity, such as hetero- and homo-dimerization, and high degrees of nitrogenation and oxygenation, as well as the capacity to be complexed with metals, incorporating additional carbon frameworks or an isoprene unit by the formation of either a linear ether or a trimethyl-hydrofuran moiety
[20][21]. Moreover, many acetone adducts of phenalenones were also reported that have an extended carbon chain at ring A, such as the acyclic diterpenoid adducts. These fungal metabolites have been demonstrated to exhibit a wide range of bioactivities, such as cytotoxic, antimicrobial, antioxidant, and anti-HIV, and tyrosinase, α-glucosidase, lipase, AchE (acetylcholinesterase), indoleamine 2,3-dioxygenase 1, angiotensin-I-converting enzyme, and tyrosine phosphatase inhibition. They are of great interest as potential lead compounds for synthetic organic chemistry because of the stability of their anions, phenalenyl radicals, and cations, as well as their interesting photophysical properties
[27][28][29].
2. Biological Activities of Phenalenones
The bioactivities of some of the reported metabolites have been investigated. In this regard, 70 metabolites have been associated with some type of biological action, including cytotoxic, antimalarial, antimycobacterial, anti-inflammatory, anti-angiogenic, immunosuppressive, and antioxidant properties, as well as IDO1, α-glucosidase (AG), ACE, tyrosinase, and PTP inhibition. This information has been discussed and listed in Table 1.
Paecilomycones A–C (
1–
3) were purified from
Paecilomyces gunnii culture extract with the aid of a preparatory HSCCC, guided by HPLC-HRESIMS, used as a tyrosinase inhibitor. Compound
1 was similar to myeloconone A2 (
4), which was formerly separated from the lichen
Myeloconis erumpens [52], except that
1 has an OH group at C-8 instead of an OCH
3 group. Compound
3 was deduced as 9-amino-6,7,8-trihydroxy-3-methoxy-4-methyl-1H-phenalen-1-one; the existence of NH
2 in
3 was confirmed by a positive purple reaction with a ninhydrin reagent in the TLC plate. They were characterized by means of spectroscopic analyses. These metabolites exhibited potent tyrosinase inhibitory potential (IC
50s 0.11, 0.17, and 0.14 mM, respectively) in the form of kojic acid (IC
50 0.10 mM), being stronger than arbutin (IC
50 0.20 mM). This influence was found to be positively related to the number of OH groups
[30] (
Figure 1).
Figure 1. The structures of compounds 1–10.
Aspergillussanones A (
5) and B (
6) were separated from
Aspergillus sp. PSU-RSPG185 broth extract. They differed from each other in the substitutions at C-8 and C-4, as well as in the C-4 configuration. The configuration of their double bonds was determined to be
E, based on signal enhancement in the NOEDIFF experiment, and the 4
S and 10′
R in
5 and 4
R and 10′
R in
6 was assigned by the CD spectrum. Only compound
5 exhibited weak cytotoxic activity toward Vero cells and KB (IC
50s 34.2 and 48.4 μM, respectively) in the resazurin microplate assay, compared to ellipticine (IC
50 4.5 and 4.1 μM, respectively), whereas
6 was inactive against the tested cell lines. Additionally, they showed no antimalarial or antimycobacterial potential toward
Plasmodium falciparum and
Mycobacterium tuberculosis when using GFP (green fluorescent protein) and the micro-culture radioisotope technique, respectively
[31] (
Figure 1).
Eleven metabolites of the herqueinone subclass, including six new derivatives,
ent-peniciherqueinone (
8), 12-hydroxynorherqueinone (
11),
ent-isoherqueinone (
13), oxopropylisoherqueinones A (
15) and B (
16), and 4-hydroxysclerodin (
27) and the known analogs,
9,
12,
17,
22, and
34 were extracted from a marine-derived
Penicillium sp. (
Figure 2). The new metabolites’ configuration was assigned, based on specific rotations and chemical modifications. Compound
17 exhibited moderate anti-inflammatory activity (IC
50 3.2 µM) towards mouse macrophage RAW 264.7 cells, compared to AMT (IC
50 0.2 µM) in the nitric oxide synthase assay. In addition,
27 exhibited moderate anti-angiogenic potential (IC
50 20.9 µM) toward HUVECs (human umbilical vascular endothelial cells), compared to sunitinib (IC
50 1.5 µM), in the tube formation assay. Furthermore,
8 and
12 moderately induced adipogenesis (IC
50 57.5 and 39.7 µM, respectively) in the hBM-MSCs (human bone marrow-mesenchymal stem cells), compared to pioglitazone (IC
50 0.69 µM), in the adiponectin production assay
[32].
Figure 2. The structures of compounds 11–22.
Lee et al. purified
18 from a culture of
Penicillium herquei FT729, derived from Hawaiian volcanic soil by LC-MS-guided chemical analysis. It was identified by spectroscopic analysis, optical rotation, and LC-MS analysis. The pretreatment of T cells with
18 remarkably reduced IL-2 production and the expression of surface molecules, including CD-25 and -69, and activated T cell proliferation after TCR-mediated stimulation, as well as abrogating the NF-κB and MAPK pathways. Therefore, it effectively down-regulated T cell activity via the MAPK pathway, which indicated its immunosuppressive potential
[53]. Furthermore,
P. herquei PSURSPG93, obtained from soil, produced a new derivative, peniciherqueinone (
7), along with the formerly separated derivatives: herqueinone (
9), deoxyherqueinone (
14), the acetone adduct of atrovenetinone (
18) (as a mixture of epimers), sclerodin (
20), and (−)-7,8-dihydro-3,6-dihydroxy-1,7,7,8-tetramethyl-5H-furo-[2′,3′,:5,6]naphtho[1,8-
bc]furan-5-one (
37). Compound
7 was structurally similar to
9, except for the disappearance of one olefinic proton signal. Its
R-configuration at C-4 was determined by an anisotropic effect and CD spectroscopy, which was opposite to
9. Compounds
9,
14, and
20 had no cytotoxic effect toward MCF-7, KB, and noncancerous Vero cell lines. In addition, only
9 exhibited mild antioxidant potential, where it inhibited OH
•, DPPH
•, and O
2•− (IC
50 0.48, 6.34, and 4.11 mM, respectively) in the hydroxyl radical, DPPH, and superoxide radical scavenging assays, respectively, in comparison with tannic acid (OH
•, IC
50 0.26), butylated hydroxytoluene (DPPH
•, IC
50 0.11), and trolox (O
2•−, IC
50 0.96 mM)
[33].
Intaraudom et al. purified the new derivatives,
25,
26,
30,
32,
36, and
39–42, together with
22 and
34, from the broth EtOAc extract of the marine-derived
Lophiostoma bipolare BCC25910 (
Figure 3). Their structures were assigned via spectroscopic analysis, whereas the C-2′, S-configuration was determined based on X-ray analysis, a chemical reaction, and a specific optical rotation negative sign. They showed no antimalarial activity toward the
P. falciparum K-1 strain and no antifungal activity toward
C. albicans. On the other hand,
25,
26,
36,
39, and
40 showed moderate antibacterial potential toward
B. cereus (MICs 12.5 µg/mL). However, other compounds were inactive against
B. cereus (concentration 25 µg/mL). Additionally, they exhibited weak cytotoxicity toward KB, MCF-7, NCI-H187, and Vero cells
[36].
Figure 3. The structures of compounds 23–37.
Macabeo et al. purified
29,
34, and
90 from a culture of
Pseudolophiostoma sp. MFLUCC-17-2081 obtained from a dried branch of
Clematis fulvicoma. Compounds
29 and
34 conferred more potent α-glucosidase inhibition (IC
50 48.7 and 120 µM, respectively) than N-deoxynojirimycin (IC
50 130.5 µM). They also potently inhibited the hydrolysis of
p-nitro-phenylbutyrate, using porcine lipase. Interestingly,
29 and
34 showed stronger inhibitory potential (IC
50s 1.0 and 3.4 µM, respectively) than orlistat (IC
50 9.4 µM). The in silico techniques employed revealed that
29 and
34 exhibited strong binding affinities to porcine pancreatic lipase and α-glucosidase through π–π and H-bonding interactions, while
90 was weakly active (IC
50 > 100 µM) toward both enzymes
[37].
Zhang et al. purified new derivatives, flaviphenalenones A–C (
45–
47), from solid cultures of
Aspergillus flavipes PJ03-11 (
Figure 4). The 6
S absolute configuration of
45 was determined by the computational ECD method. Compound
47 was a positional isomer of
46. They represented the first report of phenalenones with a directly connected C-10 isoprene unit, whereas
47 had a keto-lactone group at C-8. Compounds
46 and
47 possessed potent α-glucosidase inhibitory potential (IC
50s 94.95 and 78.96 µM, respectively) than acarbose (IC
50 685.36 µM). On the other hand,
45 displayed significant cytotoxic capacities toward MCF-7 and A549 (IC
50 10.0 and 6.6 µg/mL, respectively) compared to doxorubicin (IC
50 0.4 and 0.2 µg/mL, respectively), while
47 showed moderate cytotoxicity toward A549 (IC
50 28.5 µg/mL)
[38].
Figure 4. The structures of compounds 38–47.
Auxarthrones A–E (
49–
53) and FR-901235 (
54) were obtained from the culture of the coprophilous fungus
Auxarthron pseudauxarthron TTI-0363 (
Figure 5). Compounds
52 and
53 possessed an unusual 7a,8-dihydrocyclopenta[
a]phenalene-7,9-dione ring system. Compound
49 was separated into a mixture of racemic diastereomers; their structures were confirmed by X-ray crystallography. Compounds
49 and
51 showed moderate antifungal potential toward
C. albicans and
C. neoformans (MICs 6.4 and 3.2 μg/mL, respectively), compared to amphotericin B (MIC 0.8 μg/mL). The other phenalenones were weakly active (MIC ranging from 6.4 to 51.2 μg/mL). On the other hand, they showed no significant cytotoxic effects against MDA-MB-451 and MDA-MB-231
[39].
Figure 5. The structures of compounds 48–57.
Compound
56 obtained from the marine-derived endophytic fungus,
Coniothyrium cereale, harboring the Baltic Sea algae
Enteromorpha sp., which had unprecedented imine functionality between two carbonyls to produce an oxepane-imine-dione ring. It exhibited a moderate cytotoxic potential toward the SKM1, U266, and K562 cancer cell lines (IC
50s 75.0, 45.0, and 8.5 µM, respectively) in the MTT assay
[54]. The new phenalenone derivatives, aspergillussanones C–L (
60–
69), along with the known analog
70, were isolated from the solid culture of
Aspergillus sp. that was associated with
Pinellia ternate (
Figure 6 and
Figure 7).
Figure 6. The structures of compounds 58–65.
Figure 7. The structures of compounds 66–71.
Compounds
60–
69 are unusual acyclic diterpenoid adducts that are partly epoxidized and variously oxidized to produce diverse heterocyclic analogs. Their structures and absolute configurations were established by spectroscopic, ECD, and Mo
2(OCOCH
3)
4-induced ECD analyses. Their antibacterial effectiveness toward
Pseudomonas aeruginosa, Escherichia coli, Staphylococcus aureus, and
Bacillus subtilis was evaluated using the broth micro-dilution method. Compound
69 exhibited the most potent antibacterial potential against
B. subtilis, S. aureus, and
P. aeruginosa (MIC 4.80, 2.77, and 1.87 μg/mL, respectively), compared to streptomycin (MIC 0.34 μg/mL for
P. aeruginosa) and penicillin (MIC 0.063 and 0.13 μg/mL for
S. aureus and
B. subtilis, respectively). Compounds
65–
67 had potential versus
P. aeruginosa (MIC
50s 6.55–12.00 μg/mL). Meanwhile,
62,
63,
65, and
67 showed significant activity toward
E. coli (MIC 3.93–7.83 μg/mL)
[40].
Aspergillus sp. CPCC 400735, which is associated with
Kadsura longipedunculata, was found to biosynthesize the structurally unusual phenalenones, asperphenalenones A–E (
71–
75), these having a linear diterpene moiety that is connected to the phenalenone skeleton through a C-C bond (
Figure 8). Their structures were established from extensive NMR spectroscopic analyses, while the absolute configuration was determined based on the CD spectra. Compounds
71 and
74 exhibited anti-HIV activity (IC
50 4.5 and 2.4 µM, respectively), in comparison to lamivudine (IC
50 0.1 µM) and efavirenz (IC
50 0.0004 µM), using SupT1 cells in the luciferase assay system, while
72 and
75 exhibited weak activity (IC
50 32.6 and 22.1 µM, respectively)
[41].
Figure 8. The structures of compounds 72–78.
The new derivatives, peniciphenalenins A–F (
76–
81), along with the formerly reported
21,
28, and
33, were obtained from
Penicillium sp. ZZ901 culture, using ODS and HPLC (
Figure 9). Their structures were determined by extensive spectroscopic analysis, ECD calculation, optical rotation, and single X-ray diffraction. The analyses identified a phenalenone skeleton, fused to a trimethyl-furan ring. Compounds
28 and
33 showed antimicrobial activity toward MRSA and
E. coli (MICs 23–35 µg/mL for
28 and 7.0–9.0 µg/mL for
33). On the other hand,
21,
28, and
33 showed weak antiproliferative activity against the glioma cells (IC
50 23.24–6.93 µM), compared to doxorubicin (IC
50 1.2 and 0.47 µM, respectively)
[34].
Figure 9. The structures of compounds 73–86.
Han et al. separated three new red-colored phenalenone derivatives, peniciphenalenins G–I (
83,
31, and
84), along with coniosclerodione (
85) and (−) sclerodinol (
24) from the marine sediment-derived fungus,
Pleosporales sp. HDN1811400, using UV-HPLC guided investigation. Their absolute configurations were determined by detailed spectroscopic and ECD analyses, in addition to the chemical method. Compound
83 was the first example of a chlorinated phenalenone derivative. Compounds
24, 31,
83, and
85 showed antimicrobial potential versus
B. cereus, Proteus sp.,
M. phlei, B. subtilis, V. parahemolyticus, E. tarda, MRCNS, and MRSA (MICs 6.25–50.0 µM). Compound
85 (MIC 6.25 µM) was more active than compound
84, indicating that 19-OH reduced the activity. Notably, compounds
24,
31,
83, and
85 showed better inhibitory potential toward MRCNS and MRSA than that of ciprofloxacin, indicating their potential regarding drug-resistant strains
[35].
Basnet et al. reported the isolation of a new yellow compound, trypethelonamide A (
86), and a new dark violet-red compound, 5′,-hydroxytrypethelone (
87), along with a dark violet-red metabolites (+)-8-hydroxy-7-methoxytrypethelone (
88), (+)-trypethelone (
89), and (−)-trypethelone (
90) from the cultured lichenized fungus
Trypethelium eluteriae by using Sephadex LH-20, ODS, SiO
2, and HPLC. They were fully characterized via spectroscopic and ECD spectral analyses (
Figure 10). They showed moderate to weak cytotoxicity versus the RKO cell line (IC
50 ranged from 22.6 to 113.5 µM), compared to taxol (IC
50 0.05 µM) in the CCK8 assay, while they had no antioxidant potential in the DPPH assay (concentration 200 µM)
[42].
Figure 10. The structures of compounds 87–102.
Two new metabolites, 8-methoxytrypethelone (
93) and 5′-hydroxy-8-ethoxytrypethelone (
95), along with compounds
20,
38,
89,
91,
92, and
94 were separated from mycobiont culture of
Trypethelium eluteriae by preparative TLC and column chromatography. They were fully characterized by using spectroscopic, ECD, and X-ray analyses. Compound
89 (MIC 12.5 µg/mL) showed potent antimycobacterial potential toward
M. tuberculosis, followed by
38 and
94 (MIC 50.0 µg/mL). Moreover,
89 had moderate potential (MIC 25.0 µg/mL) toward
M.
chitae, M.
szulgai, M.
phlei, M.
flavescens, M.
parafortuitum, and
M.
kansasii. In addition, compounds
89 and
94 were active versus
S. aureus (MIC 25 µg/mL)
[55]. Funalenone (
101) was also purified as a PTP inhibitor from a marine-derived fungal strain of
Aspergillus sp. SF-5929 and was tested for its inhibitory potential on
hPTP1B
1-400 in a photocolorimetric assay using the
hPTP1B
1 enzyme. It exhibited powerful PTP1B inhibitory potential (IC
50 6.1 µM), compared to ursolic acid (IC
50 4.3 µM). It was found that
101 was a noncompetitive PTP1B inhibitor that targeted the active or allosteric site of the enzyme
[44].
Chaetosphaeronema hispidulum yielded two new phenalenones, hispidulones A (
102) and B (
103), which were assigned by spectroscopic and ECD analyses (
Figure 11).
Figure 11. The structures of compounds 103–115.
Compound
102 had a cyclohexa-2,5-dien-1-one moiety, whereas
103 possessed a hemiacetal OCH
3 group that was uncommon in phenalenone analogs. Compound
103 showed cytotoxic potential toward A-549, Huh7, and HeLa cells (IC
50 2.71, 22.93, and 23.94 μM, respectively), compared with
cis-platinum (IC
50 8.73, 5.89, and 14.68 μM, respectively), whereas
102 did not show any effect in the MTT assay
[45].
Aceneoherqueinones A (
104) and B (
105), (+)-aceatrovenetinone A (
106), and (+)-aceatrovenetinone B (
109), along with the known congeners, (+)-scleroderolide (
33), (−)-scleroderolide (
34), (−)-aceatrovenetinone B (
107), and (−)-aceatrovenetinone A (
108), were reported from the marine mangrove-derived fungus,
Penicillium herquei MA-370. Among these, compounds
104 and
105 were rare phenalenones, having a cyclic ether unit between C-2′ and C-5 (
Figure 11). Compounds
106–
109 were unstable stereoisomers, possessing configurationally labile chiral centers that were characterized by HPLC-ECD analyses, assisted by TDDFT-ECD calculations. The absolute configuration of
104 was confirmed by X-ray, while those of
105–
109 were established by ECD spectra TDDFT-ECD calculations. Compounds
104 and
105 displayed ACE (angiotensin-I-converting enzyme) inhibitory activity (IC
50s 3.10 and 11.28 μM, respectively), compared to captopril (IC
50 9.23 nM). The molecular docking study revealed that compound
104 bound well with ACE via hydrogen interactions with the residues Gln618, Ala261, Asn624, and Trp621, while
105 interacted with the Tyr360 and Asp358 residues. This difference in interactions was likely caused by the C-8 epimerization of both compounds
[46].
Penicillium herquei FT729, which is associated with Hawaiian volcanic soil, yielded herqueilenone A (
116) and erabulenols B (
117) and C (
118) (
Figure 12). Their structures were determined by spectroscopic analysis, ECD calculations, and GIAO (gauge-including atomic orbital) NMR chemical shifts. Compounds
117 and
118 exhibited significant IDO1 (indoleamine 2,3-dioxygenase 1) inhibitory activities (with IC
50 values of 13.69 and 14.38 µM, respectively), compared to epacadostat (IC
50 0.015 µM). Therefore, they can be developed into cancer immunotherapeutics. Compounds
117 and
118 also exhibited a protective effect toward acetaldehyde-induced damage in PC-12 cells and significantly increased cell viability
[47].
Figure 12. Structures of compounds 116–123.
Duclauxamide A1 (
119), a new polyketide heptacyclic-oligophenalenone dimer with an
N-2-hydroxyethyl moiety, was isolated from
Penicillium manginii YIM PH30375, which is associated with
Panax notoginseng. It belongs to the 9′S-duclauxin epimers, based on spectroscopic data analysis, single-crystal X-ray diffraction, and the computational
13C NMR-DFT method. It is structurally related to duclauxin (
120), showing the replacement of the
O-atom with the
N-containing chain, without modification, on the original carbon skeleton. It showed moderate cytotoxicity toward MCF-7, SMML-7721, A-549, HL-60, and SW480 (IC
50 ranged from 11 to 32 μM), compared to cisplatin and paclitaxel
[56]. Two new oxaphenalenone dimers, talaromycesones A (
121) and B (
122), were isolated from the marine fungus
Talaromyces sp. LF458 culture broth and mycelia. Their relative configuration was determined by NOESY spectral data. Compound
116 was the first metabolite with a 1-nor oxaphenalenone dimer framework. They exhibited significant antibacterial potential toward
S.
epidermidis and
S. aureus (IC
50s 3.70 and 5.48 μM, respectively, for
121, and 17.36 and 19.50, respectively, for
122), compared to chloramphenicol (IC
50 1.81 and 2.46 μM, respectively) in the resazurin microplate assay. They revealed no antifungal effectiveness toward
Trichophyton rubrum and
C. albicans. Moreover,
121 exhibited AchE (acetylcholinesterase) inhibition (IC
50 7.49 μM) that was more powerful than huperzine (IC
50, 11.60 μM) in the modified Ellman’s enzyme/immunosorbent assay
[50].
In the case of 9a-
epi-bacillisporin E (
124) and bacillisporins F–H (
125,
127, and
128), new oligophenalenone dimers, along with bacillisporin A (
123), were separated from a culture of
Talaromyces stipitatus (
Figure 13). Their absolute configurations and structures were determined based on spectroscopic analyses, ECD, and GIAO NMR shift calculation, followed by DP4 probability analysis. Only
128 was moderately active (IC
50 49.5 µM) toward the HeLa cell, compared to cisplatin (IC
50 10.6 µM). No effect was observed on the growth of
E. coli (IC
50 > 100 μg/mL) for all isolated compounds, while
123 displayed noticeable antibacterial potential versus
Staphylococcus hemolyticus, S.
aureus (ATCC 6538), and
Enterococcus faecalis (MICs 9.5, 5.2, and 2.4 μg/mL, respectively), compared to tetracycline (MICs 29.2, 0.05, and 0.4 μg/mL, respectively). However,
128 had an observable effect on
S. aureus (MIC 5.0 μg/mL) when using a microtiter plate assay
[51].
Figure 13. The structures of compounds 124–132.
Talaromyces verruculosus yielded two new oligophenalenone dimers, verruculosins A (
129) and B (
130), and the related known analogs, duclauxin (
120), bacillisporin F (
125), and xenoclauxin (
131) (
Figure 13). Compound
129 was a novel oligophenalenone dimer with a unique octacyclic skeleton. Compounds
129 and
130 were fully characterized by spectroscopic, X-ray crystallography, and ECD analyses as well as, optical rotation and NMR calculations. Compounds
120,
125,
129, and
131 exhibited potent CDC25B inhibitory activities (IC
50 values of 0.75, 0.40, 0.38, and 0.26 µM, respectively), compared to Na
3VO
4 (IC
50 0.52 µM). In addition,
120 and
129–
131 displayed moderate EGFRIC inhibitory activities (IC
50 values from 0.24 to 1.22 µM) in comparison to afatinib (IC
50 0.0005 µM). The results revealed that oligophenalenone dimers could be used as CDC25B inhibitor candidates
[48].
Duclauxin (
120), talaromycesone B (
122), bacillisporin G (
127), and xenoclauxin (
131) were isolated from anthill soil fungus
Talaromyces sp. IQ-313. They were evaluated for PTP (protein tyrosine phosphatases) inhibitory potential. They inhibited
hPTP1B
1-400 (IC
50 values ranging from 12.7 to 82.1 µM), in comparison to ursolic acid (IC
50 26.6 μM. Compounds
120 and
127 displayed the strongest inhibitory activity (IC
50 12.7 and 13.5 µM, respectively)
[49]. Five new polar pigments, talauxins E (
132), I (
133), L (
134), Q (
135), and V (
136), along with the previously reported 9-demethyl FR-901235 (
55), O-desmethylfunalenone (
100), and duclauxin (
120), were purified from
Talaromyces stipitatus (
Figure 14). Talauxins are unusual heterodimers that are produced from the coupling of
120 with amino acids and are closely related to duclauxamide A (
119), which was separated from
Penicillium manginii [56]. They were fully characterized via spectroscopic and X-ray analysis. Compounds
120 and
132 exhibited weak cytotoxic effectiveness (IC
50 140 and 70 μM, respectively) versus NS-1 cells, compared to 5-fluorouracil (IC
50 4.6 µM) in the resazurin microplate assay, while
132 also had weak antibacterial potential versus
B. subtilis (IC
50 265 μM), compared to clotrimazole (IC
50 0.4 μM)
[43].
Figure 14. The structures of compounds 133–139.