Several metabolites with anticancer activity and belonging to different class of natural compound were isolated from marine fungi (Table 3).

Source of novel compounds has expanded even to the marine environment [57, 58]. In fact, marine-derived fungi are associated to micorganisms as corals, sea cucumber, snails, sponges, algae and mangrove plants can be isolated from water and sediments [59,60,61]. Thus the present section describes essentially the metabolites with anticancer activity produced by marine fungi derived from different organisms or sediments. As for the previous sections the fungal marine metabolites with anticancer activity were chronologically reported.

Seven new chlorinated anthraquinones close to averantin as (1′S)-, (1′S)-6-O-methyl-, (1′S)-1′-O-methyl-, (1′S)-6,1′-O,O'-dimethyl-7-chloroaverantin, (1′S)-7-chloroaverantin-1′-butyl ether, 7-chloroaverythrin and 6-O-methyl-7-chloroaverythrin (67–73, Fig. 5) averantin, 1′-O-methylaverantin, 6-O-methylaverantin, averantin-1′-butyl ether and averythrin were isolated from the marine-derived fungus Aspergillus sp. SCSIO F063 obtained from Chinese marine sediment. Two new brominated anthraquinones and non halogenated anthraquinones, namely (1′S)-6,1′-O,O'-dimethyl- and (1′S)-6-O-methyl-7-bromoaverantin and (1′S)-6,1′-O,O'-dimethylaverantin (74–76, Fig. 5) were obtained from the fungal mycelia when sodium bromide was added to the culture medium. All the compounds were assayed for cytotoxic activity and 6-O-methyl-7-chloroaverantin (73) exhibited the strongest cytotoxicity against the tumor cell lines SF-268, MCF-7, and NCI-H460 (IC50 values of 7.11, 6.64, and 7.42 μM, respectively). The compounds were also tested for their antibacterial activities against three Gram positive bacteria as S. aureus ATCC 29213, Bacillus thuringiensis ATCC 39765 and Bacillus subtilis ATCC 6633 but up to 10 μg/6 mm paper disk no toxicity was observed [62].

Metabolites isolated from marine fungi

Chaetomium globosum, obtained from the marine fish Mugil cephalus collected in Japan, produced chaetomugilin S, dechlorochaetomugilin A and dechlorochaetomugilin D (77–79, Fig. 5). The metabolites 77–79 were tested for their cytotoxicity against the murine P388 leukemia cell line, the human HL-60 leukemia cell line, the murine L1210 leukemia cell line and the human KB epidermoid carcinoma cell line. Chaetomugilin S (77) exhibited moderate cytotoxic activity against all the cancer cell lines [63].

Bis(dethio)-10a-methylthio-3a-deoxy3,3a-didehydrogliotoxin and 6-deoxy-5a,6-didehydrogliotoxin (80 and 81, Fig. 5), close related to gliotoxin were isolated together with gliotoxin and gliotoxin G (82 and 86, Fig. 5) and their other four analogues, such as bis(dethio)bis(methylthio)gliotoxin, bis(dethio)bis-(methylthio)-5a,6-didehydrogliotoxin, 5a,6-didehydrogliotoxin, (83–85, Fig. 5), from Penicillium sp. strain JMF034, obtained from deep sea sediments of Suruga Bay, Japan. All the compounds were tested for their cytotoxicity against P388 murine leukemia cells. Gliotoxin and gliotoxin G (82 and 86) showed the strongest activity, whereas compounds 81 and 83–85 also had a significant activity while compound 80 exhibited only marginal activity. All the metabolites were also evaluated for their inhibitory activity against HMT G9a and HMT Set7/9 (lysine-specific histone methyltransferase for lysine 4 in histone H3) and compounds with a disulfide or tetrasulfide bond (82, 85, and 86) possessed a high inhibitory activity. Compound 81, which also has a disulfide bond, had a weaker activity suggesting that the hydroxy group at C-6 interfers with the G9a inhibitory activity. Any compounds inhibited HMT Set7/9 at 100 μM [64].

Aspergiolide A (87, Fig. 5), a polyketide, was isolated from Aspergillus glaucus HB 1–19, a marine-derived fungus [62]. Compound 87 showed selective cytotoxic activity against A-549, HL-60, BEL-7402, and P388 cell lines with IC50 of 0.13, 0.28, 7.5, and 35.0 μM, respectively [65].

Auranomides A and B and C (88–90, Fig. 5), two alkaloids and a quinazolin-4-one substituted with a pyrrolidin-2-iminium moiety, were isolated together with auranthine and aurantiomides C from Penicillium aurantiogriseum, which is a marine-derived fungus, obtained from marine mud of the Bohai Sea, China. Compounds 88–90 were tested for their anticancer activity against several cancer cell lines and showed only a moderate cytotoxicity against human tumor cells. Auranomides B (89) exhibited the stronger activity against HEPG2 cells (IC50 value of 0.097 μmol/mL) [67].

Penicacids A-C (91–93, Fig. 6), three phenolic acid derivatives, were isolated together with mycophenolic acid and its 4'-hydroxy-derivative from the fungus Penicillium sp. SOF07, which was obtained from a Chinese marine sediment [68]. All the compounds were tested in the inhibition of IMPDH (type II) activity, which is an essential rate-limiting enzyme in the purine metabolic pathway [69]. IMPDH affects the size of the guanine nucleotide pool which, in turn, controls many physiological processes including replication, transcription, signaling and glycosylation [70] and thus it is an important drug target for immunosuppressive, antiviral and cancer chemotherapy [71]. The results obtained showed that compounds 91–93 and the two analogues inhibited IMPDH with IC50 values of 28.86, 6.43, 73.24, 0.63, and 1.79 μM, respectively. These results prompted to use the same compounds to assay their splenocyte T lymphocyte proliferation. The immunosuppresive activities of all the other compounds, at the cellular level, paralleled their IMPDH inhibitory activity, with the exception of glycosylated acid 92. Thus SAR results from both bioassays showed that the HO-C(7), the C-2ʹ/C-3ʹ olefin, and the absence of the HO-C-4ʹ are important structural features in the immunosuppresive activities exhibited by this class of acid compounds at both the enzymatic and cellular levels [68].

Metabolites isolated from marine fungi

6-O-Desmethyldechlorogriseofulvin and 6ʹ-hydroxygriseofulvin (94 and 95, Fig. 6) were isolated from a solid rice culture of Nigrospora sp. MA75, which is an endophytic fungus collected from Chinese marine semi-mangrove plant Pongamia pinnata. When the fungus was grown in liquid culture containing NaCl produced some other already known metabolites such as dechlorogriseofulvin and griseofulvin, the main metabolites, tetrahydrobostrycin, 4-deoxytetrahydrobostrycin, 3,8-dihydroxy-6-methoxy-1-methylxanthone, 3,6,8-trihydroxy-1-methylxanthone and griseophenone C. When NaI was added to the same liquid conditions, the fungus produced 2,3-didehydro-19a-hydroxy-14-epicochlioquinone B (96, Fig. 6). [72]. All the compounds were tested for their cytotoxicity and compound 96 showed activity against MCF-7, SW1990, and SMMC7721 cell lines (IC50 values of 4, 5, and 7 μg/ml, respectively), and moderate activity against HepG2, NCI-H460, and DU145 cell lines (IC50 values of 20, 11, and 17 μg/ml, respectively). It showed the stronger activity toward SW1990 cell line [72]. All the compounds were also assayed against the bacteria S. aureus (MRSA), E. coli, Pseudomonas aeruginosa, Pseudomnas fluorescens and Staphylococcus epidermidis, and the fungi, C. albicans, Valsa mali and Stemphylium solani. Compound 96 showed a significant activity against all the tested bacteria; MIC values measured were 8, 4, 4, 0.5, and 0.5 μg/ml, for MRSA, E. coli, P. aeruginosa, P. fluorescens, and S. epidermidis,respectively. Griseophenone C strongly inhibited MRSA, E. coli, P. aeruginosa, and P. fluorescens (MIC values of 0.5, 2, 0.5, and 0.5 μg/ml, respectively). Tetrahydrobostrycin exhibited significant activity against MRSA and E. coli (MIC values of 2 and 0.5 μg/ml, respectively), while its analog, 4-deoxytetrahydrobostrycin, showed activity only against E. coli with a MIC value of 4 μg/ml [72]. This results suggested that the presence of the HO-C(4) might be an important feature for the activity against MRSA. Furthermore, griseofulvin, only showed moderate activity against V. mali and S. solani (MIC values of 16 μg/ mL), while the other derivatives exhibit a weaker or no antifungal activities. The activity of griseofulvin could be due to its planar structure and spatial configuration [72]. In fact, griseofulvin is an antibiotic fungicide and is now used for the treatment of human mycotic diseases, in veterinary and plant system [73].

A fumiquinazoline K, 6β,16β-Diacetoxy-25-hydroxy-3,7-dioxo-29-nordammara-17(20)-dien-21,24-lactone (97 and 98, Fig. 6), an alkaloid and a nordammarane triterpenoid, were isolated together with three known diketopiperazines including spirotriprostatin A, 6-methoxyspirotriprostatin B and tryptoquivaline from Aspergillus fumigatus KMM 4631 associated with the soft coral Sinularia sp. To a third diketopiperazione was not assigned a common name but it is (1S,2S,3S,5aS,10aR)-1,10a-dihydroxy-6ʹ-methoxy-3-(2-methylprop-1-en-1-yl)-5a,6,7,8-tetrahydro-1H-spiro[dipyrrolo[1,2-a:1ʹ,2ʹ-d]pyrazine-2,2ʹ-indoline]-3ʹ,5,10(3H,10aH)-trione (99, Fig. 6) [74].

The marine material was collected in Kunachir island, Kuril islands, Russia. Compounds 99, spirotriprostatin A and 6-methoxyspirotriprostatin B showed weak cytotoxic activity against cytoplasm non-specific esterase in Ehrlich carcinoma cells. Compound 99 also caused early apoptosis of the same cells using not toxic concentration range [74].

Fischeacid and fischexanthone (100 and 101, Fig. 6) were isolated from the culture of a marine-derived fungus Neosartorya fischeri strain 1008F1, together with sydowinin A, sydowinin B AGI-B4, chrysophanol, emodin, 5ʹ-deoxy-5ʹ-methylamino-adenosine, adenosine and 3,4-dihydroxybenzoic acid. All compounds were tested for their cytotoxic and antiphytoviral activity under the concentration of 200 μg/mL. Among all, AGI-B4 showed a potent inhibition of human gastric cancer cell line SGC-7901 (IC50 0.29 ± 0.005 mmol/L) and hepatic cancer cells BEL-7404 (IC50 0.31 ± 0.004 mmol/L) proliferation. The same compound and 3,4-dihydroxybenzoic acid, the main fungal metabolites, showed antiphytoviral activity with effective inhibition of the replication of TMV (Tobacco Mosaic Virus) (IC50 values of 0.26 ± 0.006 and 0.63 ± 0.008 mmol/L, respectively) [75].

Expansols C-F and 3-O-methyldiorcinol (102–105 and 106, Fig. 6), which are polyphenols containing both phenolic bisabolane and diphenyl ether moieties, and one a diphenyl ether derivative, were isolated from Penicillium expansum 091006. This fungus is an endogenous microrganism of the mangrove plant Excoecaria agallocha (Euphorbiaceae). Expansols A and B, diorcinol, and S-(+)-sydonic acid, (+)-(7S)-7-O-methylsydonic acid, butyrolactone I and V, WIN 64 821, 3,7-dihydroxy-1,9-dimethyldibenzofuran, orcinol, 2,4-dimethoxyphenol and 4-hydroxybenzoic acid were isolated from the same fungal culture filtrates. Among all the compounds assayed for the cytotoxic activity, expansols C and E (102 and 104) showed a weak cytotoxicity against the HL-60 cell lines (IC50 values of 18.2 and 20.8 µM, respectively). These results suggested that diphenyl ether substituted phenolic bisabolanes with a Δ7 double bond in the side chain are slightly lesser cytotoxic to HL-60 cell lines than derivatives having the OH or the OCH3 at C-7 [76].

Toluquinol (107, Fig. 6), a methylhydroquinone was isolated Penicillium sp. HL-85-ALS5- R004. Toluquinol, tested in the micromolar range, strongly inhibited activated endothelial cells and thus the growth of endothelial and tumor cells in culture. These effect seemed due to the apoptosis induction as the endothelial cell death is mediated via apoptosis after a cell cycle block and caspase activation. Furthermore, these results showed that toluquinol has antiangiogenic effects in vitro and in vivo and this activity is partly due to the suppression of the VEGF and FGF-induced Akt activation of endothelial cells [77].

JBIR-27, petasol, sporogen AO-1, and dihydro-AO-1 (108–111, Fig. 6), four sesquiterpenes, were isolated from Penicillium citrinum obtained from a Chinese marine coral of the Zoantharia order. AO-1 (110) showed antiyeast activity against C. albicans (MIC 4.0 mM) while it and its dihydro AO-1 (111) showed toxicity against Ehrlich carcinoma cells (ED50 of 0.9 and 0.4 mM, respectively). JBIR-27 (108) and petasol (109) were not toxic [78].

Aculeatusquinones A-D (112–115, Fig. 7) were isolated from Aspergillus aculeatus, a marine-derived fungus, together wih 5aS,6S,7S)-3,7-dihydroxy-6-methoxy-1,4,6,9tetramethyl-6,7-dihydro-5aH-dibenzo[b,e][1,4]dioxepine-8,11-dione, 3,8-dihydroxy-1,4,6,9-tetramethyldibenzo[b,e][1,4]dioxepin-11-one,  4-O-demethylbarbatic acid, atraric acid and 2,5-dimethyl-1,3-benzenediol. Aculeatusquinones A and D (112 and 115) showed cytotoxic effects on the HL-60, K562, and A-549 cell lines, (IC50 values ranging from 5.4 to 76.1 µM) [79].

Metabolites isolated from marine fungi

Penitrems A, B, D, E and F, paspaline and emnidole SB (116–123, Fig. 7) were isolated from Penicillium commune collected from the Kuwaiti coast. When KBr was added to the culture medium growth also 6-bromopenitrem B and 6-bromopenitrem E (124 and 125, Fig. 7) were obtained. All the metabolites showed good antiproliferative, antimigratory and antiinvasive activity against human breast cancer cells. Penitrem B (117) also exhibited a good toxicity in the NCI-60 DTP human tumor cell line screen. The BK channel inhibitory potential of paspaline, emnidole SB and 6-bromopenitrem B (122–124), was tested using the nematode Caenorhabditis elegans as an in vivo model. The same test was used to evaluated the toxicity of compounds 116–124.The BK channel inhibition in C. elegans appeared associated with an abnormal behavior of worm locomotion in terms of increased reversals, i.e., the number of times a worm stops and reverses its direction, which can be easily assessed and quantified. Among all penitrems, penitrem A (116), was the most potent tremorgen and caused a reversal pattern comparable to that of the knockout strain. 6-Bromopenitrem E (125) had the same inhibitory activity indicating no specific halogenation preference for the activity, while emindole SB (123), was not active. Considering their antiproliferative activity against the breast cancer MCF-7 a pharmacophore model was produced to justify some structural relationships of 116–124. Thus paspaline (122) and emindole SB (123), which are the less complex biosynthetic precursors, were identified as potential tools suitable for future studies [80].

Penicitrinone E and penicitrinol J (126 and 127, Fig. 7), two citrinin dimers, and two monomer derivatives penicitrinol K and citrinolactone D (128 and 129, Fig. 7) were isolated together penicitrinone A, penicitrinone B, citrinolactone B, citrinin, 2,3,4-trimethyl-5,7-dihydroxy-2,3-dihydrobenzofuran and phenol A from Penicillim sp., colleceted from the Taiwan Strait, China. All the compounds were assayed against the HeLa and HepG-2 cell lines and had no remarkable cytotoxic activity at 10 μg/mL. The antibiotic and fungicide activity of compounds 126–129 was tested against S. aureus, E. coli, C. albicans and Aspergillus niger and only penicitrinol J and penicitrinol K (127 and 128) exhibited weak antimicrobial activity against S. aureus CMCC26003 [81].

2-(4-Hydroxybenzoyl)quinazolin-4(3H)-one (130, Fig. 7) was isolated together with 2-(4-hydroxybenzyl)quinazolin-4(3H)-one, rubinaphthin A, citreorosein and methyl 4-hydroxyphenylacetate from Penicillium oxalicum 0312F1. The compounds were tested for their anti-phytoviral activity, at 200 μg/mL, and 2-(4-hydroxybenzyl) quinazolin-4(3H)-one and methyl 4-hydroxyphenylacetate showed a strong inhibition of the replication of TMV (IC50 values 100.80 and 137.78 μg/mL, respectively), while 2-(4-hydroxybenzoyl) quinazolin-4(3H)-one and rubinaphthin A exhibited moderate inhibitory activity. Among all the compounds tested at 200 μg/mL only 2-(4-hydroxybenzoyl)quinazolin-4(3H)-one exhibited moderate inhibitory activity of human gastric cancer cell SGC-7901 proliferation [82].

7,8-Dihydroxy-3,5,7-trimethyl-8,8a-dihydro-1H-isochromen-6(7H)-one and 6-(hydroxylmethyl)-2,2-dimethyl-3,4-dihydro-2H-chromene-3,4-diol (131 and 132, Fig. 7), two polyketides, were isolated together with [12]-cytochalasin from culture filtrates Eutypella scoparia FS26, a marine sediment-derived fungus obtained from the South China Sea. The three compounds were tested for their cytotoxic activity against SF-268, MCF-7 and NCI-H460, three human tumour cell lines, and [12]cytochalasin showed moderate cytoxiticity towards SF-268 and MCF-7 (IC50 values of 35.4 and 47.2 μM, respectively), while the two polyketides had not appreciable toxicity [83].

Dankastatin C (133, Fig. 7), a new polyketide tyrosine derivative, was isolated from the Gymnascella dankaliensis, a sponge-derived fungus, together with the steroid demethylincisterol A3, which was also previously produced by a Homaxinella marine sponge [84]. The compounds were assayed against the murine P388 lymphocytic leukemia cell line and dankastatin C (133) showed an ED50 value (57 ng/mL) which is similar to that of 5-fluorouracil (ED50 78 ng/mL), which is the anticancer drug used as a positive control. The steroid had significant cytotoxicity (ED50 value of 1.0 μg/mL). The strong cytotoxic effect of the gymanastatin class of compounds probably could derived from conjugated ketones as previouslyo bserved in the close gymnastatin A [85] and dankastatin A [86] (134 and 135, Fig. 7), previously isolated from the same fungus, and showing ED50 values of 18 and 150 ng/mL, respectivly. Consequently, the potent cytotoxicity of compound 133 could be due to the presence of a conjugated ketone that this metabolite might produce in the bioassay system [87].

Aszonalenin analogue and sartorypyrone A (136 and 137, Fig. 8) were isolated from the culture of the soil fungus Neosartorya fischeri (KUFC 6344) together with aszonalenin acetylaszon-alenin, 13-oxofumitremorgin B, aszonapyrone A and helvolic acid (138–142, Fig. 8). Neosartorya laciniosa (KUFC 7896), obtained from diseased coral, synthesized aszonapyrone A (141), aszonapyrone B, tryptoquivaline L and 3′-(4-oxoquinazolin-3-yl)spiro[1H-indole-3,5'-oxolane]-2,2'-dione, (143–145, Fig. 8), while Neosartorya tsunodae (KUFC 9213), obtained from sponge, produced sartorypyrone B (146, Fig. 8) and helvolic acid (142). Among all the metabolites isolated aszonalenin derivatives, sartorypyrone A, 13-oxofumitremorgin B, aszonapyrone A, aszonapyrone B and sartorypyrone B (136, 138, 139, 137, 140, 141, 143 and 146), were tested against MCF-7, NCI-H460 and A375-C, brest, brest adenocarcinoma, non small cell lung cancer and melanoma cell lines, respectively [88].

Metabolites isolated from marine fungi

Aszonapyrone A (141) apperared to be the most growth inhibitory compound of all the three cell lines (GI50 = 115.0 ± 20.0, 123.3 ± 11.5 and 68.9 ± 129 μM for MCF-7, NCI-H460 and A375-C5, respectively). Aszonapyrone B (143), which differs from aszonapyrone A (141) for the hydrolysis of acetoxy group at C-3, was inactive also at the highest concentration tested (150μM). Sartorypyrone B (146) was lesser active than aszonapyrone A (141), with GI50 17.8 ± 7.4, 20.5 ± 2.4 and 25.0 ± 4.4 μMfor MCF-7, NCI-H460 A375-C5, respectively. Furthermore, sartorypyrone A (137), which include a monocyclic diterpene moiety, showed a selective inhibitory activity similar to that of sartorypyrone B (146) against A375-C5 cells (GI50 = 21.5 ± 1.9 μM), and was less active against MCF-7 and NCI-H460 (GI50 = 46.3 ± 7.6 and 37.3 ± 4.0 μM, respectively). Finally, the three aszonalenin derivatives 136, 138 and 139 were no toxic against all the three cell lines at the highest concentration tested (150 μM), while13-oxofumitremorgin B (140) showed only weak inhibitory activity [88].

Trichoderiol C, citrinoviric acid and penicillenol D (147–149, Fig. 8) were isolated from the marine-derived fungus Trichoderma citrinoviride, collected from sediment of the Min River estuary in China, together with trichoderiol A, lignoren, penicillenol B1, penicillenol B2, cyclo-(Leu-Pro), cyclo-(Ile-Pro) and cyclo-(Phe-Pro). Among these compounds, 148 and 149 showed moderate cytotoxic activity against A-375 cell line, with IC50 values of 85.7 and 32.6 μM, respectively [89].

(+)-6-O-Demethylpestalotiopsin A, (+)-6-O-demethylpestalotiopsin C and (−)-6-O-demethylpestalotiopsin B (150–152, Fig. 8) were isolated from the marine-derived fungus Ascotricha sp. ZJ-M-5, collected on the coastal beach in Fenghua County, Zhejiang Province, China together with 1,3,6-trihydroxy-8-methylxanthone. The compounds 150–152 were tested for their growth inhibitory activity against HL-60 and K562 cells and metabolite 152 was not toxic (GI50 > 100 μM). Compounds 150 and 151 showed higher inhibition than the positive control cisplatin (GI50 = 13.4 ± 1.9 μM against HL-60 and 19.1 ± 2.3 mM against K562) with GI50 values of 6.9 ± 0.4 μM (HL-60) and 10.1 ± 0.9 μM (K562) for 150 and 8.5 ± 0.7 μM (HL-60) and 12.3 ± 1.1 μM (K562) for 151 [90]

Penicimutalides A-G (153–159, Fig. 8) were isolated from a mutant of a marine-derived Penicillium purpurogenum together with fellutamide B, fellutamide C, 1ʹ-O-methylaverantin, averantin. Their cytotoxic activity was tested against human cancer K562, HL-60, HeLa, BGC-823, and MCF-7 cells. The seven penicimutalides A-G (153–159) and fellutamide C weakly inhibited these cells to varying extents with inhibition rate (IR%) values as well as the five polyketides such as 1'-O-methylaverantin, averantin, averufin, nidurufin and sterigmatocystin against the K562 cells with showed IR% values of 11.6%, 51.9%, 37.9%, 25.5% at 100 µg/mL, and 37.5%) at 50 µg/mL. Instead, fellutamide B exhibited stronger cytotoxicity than penicimutalides A-G (153–159) and the other metabolites (IC50 values of 29.1, 59.9, 59.5, 77.9 and 43.3 µg/mL for K562, HL-60, HeLa, BGC-823 for MCF-7 cell lines, respectively). The positive control 5-flurouracel (5-FU) inhibited the same cell lines with the IR% values of 48.5%, 38.2%, 37.4%, 47.8% and 47.4% at 100 µg/mL [91].

Chondrosterins I and J (160 and 161, Fig. 9) were isolated from the marine fungus Chondrostereum sp., obtained from soft coral Sarcophyton tortuosum, collected from the Hainan Sanya National Coral Reef Reserve, China. Compounds 160 and 161 were assayed for their cytotoxicity against human nasopharyngeal cancer cell lines CNE-1 and CNE-2.Chondrosterins J (161) showed potent cytotoxic activity against both cell lines (IC50 values of 1.32 and 0.56 μM, respectively) which was stronger than that of chondrosterin A (CNE-2: 4.95 μM), hirsutanol A (CNE-1: 10.08 μM; CNE-2: 12.72 μM), and incarnal (CNE-1: 34.13 μM; CNE-2: 24.87 μM). Chondrosterin I (160), was not toxic (IC50 values > 200 μM) [92].

Metabolites isolated from marine fungi

Scopularides A and B (162 and 163, Fig. 9), two cyclodepsipeptides, were isolated from Scopulariopsis brevicaulis LF580, which was collected from the inner tissue of the marine sponge Tethya aurantium. The two compounds showed specific activity against the pancreatic (Colo357, Panc89) and the colon (HT29) tumor cell lines. Thus the development of a sustainable biotechnological production process for these compounds appeared to be an important goal. A robust and reliable screening system generally applicable for the search of secondary metabolites in fungi was realized and a mutagenesis experiment was chosen as a respective application example [93].

Pseurotin A, pseurotin D and pseurotin FD-838 (164–166, Fig. 9), hetero-spirocyclic γ-lactams, and the alkaloids fumitremorgin C, 12,13-dihydroxy fumitremorgin C, methylsulochrin and bis(dethio)bis(methylthio)gliotoxin (167–170, Fig. 9) were isolated from a strain of Aspergillus sp. (BRF 030). The fungus was obtained from the sediments collected in the northeast coast of Brazil. All compounds were tested for their cytotoxicity against the tumour cell line HCT-116 (human colon carcinoma). Pseurotin A (164) showed an IC50 of 72 μM which did not justify the high toxicity showed by corresponding mother-fraction, while pseurotin D (165) had a comparable activity with IC50 of 85 μM. The diketopiperazines fumitremorgin C and 12,13-dihydroxy-fumitremorgin C (167 and 168), appeared to be the most active compounds with an IC50 value of 15.17 and 4.53 μM, respectively. Pseurotin FD-838, methylsulochrin and bis(dethio)bis(methylthio)gliotoxin (166, 169 and 170) showed no toxicity in the range of concentrations tested (IC50 > 120 μM) [94].

4-Me-6E,8E-hexadecadienoic acid was isolated from marine-derived fungus Clonostachys rosea collected from sediments of the river Loire estuary (France). Thes fatty acid reduced viability of MCF-7 breast cancer cells in a dose dependent manner (up to 63%) at physiological free fatty acid human plasma concentration (100 μM). Studies were also performed on its mode of action investigating the reduction of gene expression of the acetyl CoA carboxylase (ACC) and the fatty acid synthase (FAS). At 50 μM, inhibition of 50% and 35% of mRNA gene expression were observed for ACC and FAS, respectively [95].

Curvularin, citrinin, penicitrinone A, erythro-23-O-methylneocyclocitrinol and 22E-7α-methoxy-5α,6α-epoxyergosta-8(14),22-dien-3β-ol (171–175, Fig. 9) were isolated from a mutant of wild-type Penicillium purpurogenum G5, which was collected at the tideland of Bohai Bay around Lüjühe in Tanggu District of Tianjin, China. All the compounds were tested for their cytotoxicity against the human cancer K562, HL-60, HeLa and BGC-823 cell lines, which growth was inhibited in the ranging values (IR%) 27.5% to 88.5% at the 100 μg/mL, while the positive control docetaxol inhibited these cell lines with the IR% values of 79.9% 86.9% 78.6% and 61.5% at 100 μg/mL [96]

Rhizovarins A-F (176–181, Fig. 9) were isolated from the fungus Mucor irregularis (formerly known as Rhizomucor variabilis) collected from mangrove plant Rhizophora stylosa, which grows in Hainan Island, China. Some indole-diterpenes, including secopenitrem D, PC-M4, penijanthine A, paxilline, 1′-O-acetylpaxilline, 4b-deoxy-1′-O-acetylpaxilline, 3-deoxo-4b-deoxypaxilline and 3b-hydroxy4b-desoxypaxilline were obtained from the same fungus. Among all the rhizovarins, compounds 176–178 represent the most complex members of the reported indole-diterpenes for the presence of an unusual acetal linked to a hemiketal (176) or a ketal (177 and 178) in an unprecedented 4,6,6,8,5,6,6,6,6-fused indole-diterpene ring system. The compounds were tested for their antitumor activity against the human A-549 and HL-60 cancer cell lines. Compounds 176, 177, penitrems A, B and F and 3b-hydroxy4b-desoxypaxilline showed activity, while rhizovarin E (180) showed toxicity only against the A-549 cancer cell line. The other indole-diterpenes showed weak or no activity (IC50 > 10 μM) against these two cell lines. In this screening, all of the chlorinated compounds (176, 177, penitrems A, B and F and 3b-hydroxy4b-desoxypaxilline) exhibited toxicity against both A-549 and HL-60 cancer cell lines. On the other hand, the chlorinated derivatives except 176, showed stronger activity than their chlorine-free analogues. These results indicated that the chlorine might be an essential feature for the activity against the cell targets. Among the paxilline-type indole-diterpenes only 3b-hydroxy-4b-desoxypaxilline, in which the 13-hydroxy group is missing and the 10-keto group is replaced by 10β-hydroxy group, showed activitiy against the two cell lines. This result also suggested that the 10β-hydroxy is an essential feature to impart the activity of the paxilline type indole-diterpenes as the analogue 3-deoxo-4b-deoxypaxilline was inactive [97].

Aurasperone A, fonsecinone D, aurasperone F, fonsecinone B, aurasperone B, aurasperone C, fonsecinone A, asperpyrone A, fonsecinone C, asperpyrone D, asperpyrone E (182–