Potential Pharmacological Resources: Natural Bioactive Compounds from Marine-Derived Fungi

In recent years, a considerable number of structurally unique metabolites with biological and pharmacological activities have been isolated from the marine-derived fungi, such as polyketides, alkaloids, peptides, lactones, terpenoids and steroids. Some of these compounds have anticancer, antibacterial, antifungal, antiviral, anti-inflammatory, antioxidant, antibiotic and cytotoxic properties. This review partially summarizes the new bioactive compounds from marine-derived fungi with classification according to the sources of fungi and their biological activities. Those fungi found from 2014 to the present are discussed.


Introduction
The oceans, which cover more than 70% of the earth's surface and more than 95% of the earth's biosphere, harbor various marine organisms. Because of the special physical and chemical conditions in the marine environment, almost every class of marine organism displays a variety of molecules with structurally unique features. However, unlike the long historical medical uses of terrestrial plants, marine organisms have a shorter history in pharmacological application [1]. In recent years, a significant number of novel metabolites with pharmacological potential have been discovered from marine organisms, such as polyketides, alkaloids, peptides, proteins, lipids, shikimates, glycosides, isoprenoids and hybrids, which exhibit biological activity including anticancer, antitumor, antiproliferative, antimicrotubule, cytotoxic, photo protective, as well as antibiotic and antifouling properties [2]. Among them, marine microorganisms, such as bacteria, actinomycetes, fungi and cyanobacteria have attracted more attention as potential lead compound producers. In comparison to marine invertebrates, they are a renewable and a reproducible source, as they can be cultured and can even be envisaged as amazing microbial factories for natural products [3].
Previously, scientists always focused on actinomycetes for their abilities to produce antibiotics. In fact, many fungal metabolites in the pharmaceutical market indicates the potential of microorganisms as valuable sources of lead drugs, e.g., the antibiotic polyketide griseofulvin (Likuden M ® ), the antibacterial terpenoid fusidic acid (Fucidine ® ), semi-synthetic or synthetic penicillins and cephalosporins, macrolides, statins as well as the ergot alkaloids such as ergotamine (Ergo-Kranit ® ) [4]. In 1949, the first secondary metabolite isolated from a marine-derived fungal strain, famous cephalosporin C, was produced by a culture of a Cephalosporium sp. isolated from the Sardinian coast. However, this was a more or less accidental discovery.
Despite the discovery of such important drug from marine fungi, the number of bioactive natural products originated from marine fungi increased extremely slowly. It is only from the late 1980s that researchers have focused on marine-derived fungi. In fact, marine-derived fungi are very important sources for novel bioactive secondary metabolites that could potentially be used as  The extract of a strain of Aspergillus versicolor MF359 (from the sponge of Hymeniacidon perleve, Bohai Sea, China) yielded one new secondary metabolites, named 5-methoxydihydrosterigmatocystin (10). Compound 10 showed potent activity against Staphylococcus aureus (S. aureus) and Bacillus subtilis (B. subtillis) with MIC values of 12.5 and 3.125 µg/mL, respectively ( Figure 3) [9].
A new chevalone derivative, named chevalone E (12), was isolated from the ethyl acetate extract of the undescribed marine sponge-associated fungus Aspergillus similanensis KUFA 0013, which was collected from the Similan Islands, Phang Nga Province, Southern Thailand. Compound 12 was found to show synergism with the antibiotic oxacillin against methicillin-resistant S. aureus ( Figure 3) [11].
Xylarianaphthol-1 (13), a new dinaphthofuran derivative, was isolated from an Indonesian marine sponge-derived fungus of order Xylariales on the guidance of a bioassay using the transfected human osteosarcoma MG63 cells (MG63 luc+ ). Compound 13 activated p21 promoter stably transfected in MG63 cells with dose-dependent pattern. Expression of p21 protein in the wild-type MG63 cells was also promoted by xylarianaphthol-1 treatment, indicating compound 13 was expected to contribute to cancer prevention or treatment ( Figure 3) [12].
A new polyketide with a new carbon skeleton, lindgomycin (14), was extracted from mycelia and culture broth of different Lindgomycetaceae strains, which were isolated from a sponge of the Kiel Fjord in the Baltic Sea (Germany) and from the Antarctic. Compound 14 showed antibiotic activities with IC 50 value of 5.1 (˘0.2) µM against MRSA ( Figure 3) [13].  The extract of a strain of Aspergillus versicolor MF359 (from the sponge of Hymeniacidon perleve, Bohai Sea, China) yielded one new secondary metabolites, named 5-methoxydihydrosterigmatocystin (10). Compound 10 showed potent activity against Staphylococcus aureus (S. aureus) and Bacillus subtilis (B. subtillis) with MIC values of 12.5 and 3.125 μg/mL, respectively ( Figure 3) [9].
A new chevalone derivative, named chevalone E (12), was isolated from the ethyl acetate extract of the undescribed marine sponge-associated fungus Aspergillus similanensis KUFA 0013, which was collected from the Similan Islands, Phang Nga Province, Southern Thailand. Compound 12 was found to show synergism with the antibiotic oxacillin against methicillin-resistant S. aureus ( Figure 3) [11].
Xylarianaphthol-1 (13), a new dinaphthofuran derivative, was isolated from an Indonesian marine sponge-derived fungus of order Xylariales on the guidance of a bioassay using the transfected human osteosarcoma MG63 cells (MG63 luc+ ). Compound 13 activated p21 promoter stably transfected in MG63 cells with dose-dependent pattern. Expression of p21 protein in the wild-type MG63 cells was also promoted by xylarianaphthol-1 treatment, indicating compound 13 was expected to contribute to cancer prevention or treatment ( Figure 3) [12].
A new polyketide with a new carbon skeleton, lindgomycin (14), was extracted from mycelia and culture broth of different Lindgomycetaceae strains, which were isolated from a sponge of the Kiel Fjord in the Baltic Sea (Germany) and from the Antarctic. Compound 14 showed antibiotic activities with IC50 value of 5.1 (±0.2) μM against MRSA (Figure 3) [13].
Two nucleoside derivatives (23)(24) were isolated from the fungus Aspergillus versicolor which was derived from the gorgonian Dichotella gemmacea in the South China Sea. Compounds 23/24 (a mixture of compound 23:compound 24 at a ratio of 7:10) exhibited selective antibacterial activity against Staphylococcus epidermidis with an MIC value of 12.5 μM ( Figure 6) [17].  Two new sulfur-containing benzofuran derivatives, eurothiocin A and B (25 and 26) were isolated from the fungus Eurotium rubrum SH-823 which was obtained from a Sarcophyton sp. soft coral in the South China Sea. The compounds (25 and 26) shared a methyl thiolester moiety, which was quite rare in natural secondary metabolites. Both of them exhibited more potent inhibitory effects against α-glucosidase activity than acarbose, which was the clinical α-glucosidase inhibitor. Further mechanistic analysis demonstrated that both of them exhibited competitive inhibition characteristics ( Figure 7) [18].
Chondrostereum sp. was isolated from the inner tissue of a soft coral Sarcophyton tortuosum, which was collected from the Hainan Sanya National Coral Reef Reserve, China. When this fungus was cultured in a liquid medium containing glycerol as the carbon source, a new metabolite, chondrosterin 27 was obtained. Compound 27 exhibited potent cytotoxic activities against the cancer cell lines CNE-1 and CNE-2 with the IC 50 values of 1.32 and 0.56 µM (Figure 7) [19]. Two new sulfur-containing benzofuran derivatives, eurothiocin A and B (25 and 26) were isolated from the fungus Eurotium rubrum SH-823 which was obtained from a Sarcophyton sp. soft coral in the South China Sea. The compounds (25 and 26) shared a methyl thiolester moiety, which was quite rare in natural secondary metabolites. Both of them exhibited more potent inhibitory effects against α-glucosidase activity than acarbose, which was the clinical α-glucosidase inhibitor. Further mechanistic analysis demonstrated that both of them exhibited competitive inhibition characteristics (Figure 7) [18].
Chondrostereum sp. was isolated from the inner tissue of a soft coral Sarcophyton tortuosum, which was collected from the Hainan Sanya National Coral Reef Reserve, China. When this fungus was cultured in a liquid medium containing glycerol as the carbon source, a new metabolite, chondrosterin 27 was obtained. Compound 27 exhibited potent cytotoxic activities against the cancer cell lines CNE-1 and CNE-2 with the IC50 values of 1.32 and 0.56 μM (Figure 7) [19]. A steroid derivative, compound 28 was isolated from the fermentation broth of a gorgonian-derived Aspergillus sp. fungus. The fungus was isolated from the inner part of the fresh gorgonian M. abnormalis, which was collected from the Xisha Islands coral reef of the South China Sea. Compound 28 inhibited the larval settlement of barnacle Balanus amphitrite with EC50 18.40 ± 2.0 μg/mL (Figure 7) [20].
A new diphenyl ether derivative, talaromycin A (29) was isolated from a gorgonian-derived fungus, Talaromyces sp. The fungal strain was isolated from a piece of fresh tissue from the inner part of the gorgonian Subergorgia suberosa, collected from the Weizhou coral reef in the South China Sea. Compound 29 showed potent antifouling activities against the larval settlement of the barnacle Balanus amphitrite with the EC50 value 2.8 ± 0.2 μg/mL ( Figure 7) [21].

Starfish
Liang et al. [22] investigated the influence on secondary metabolites with variety of cultivation parameters of marine fungus, Neosartorya pseudofischeri, which was isolated from the inner tissue of starfish Acanthaster planci. Glycerol-peptone-yeast extract (GlyPY) and glucose-peptone-yeast extract (GluPY) media were applied to culture this fungus. A novel gliotoxin (30) was produced with GluPY medium. Compound 30 displayed significant inhibitory activities against three multidrug-resistant bacteria, S. aureus (ATCC29213), MRSA (R3708) and Escherichia coli (E. coli) (ATCC25922), as well as cytotoxicities against some cell lines including human embryonic kidney (HEK) 293 cell line and human colon cancer cell lines, HCT-116 and RKO (a poorly differentiated colon carcinoma cell line) ( Figure 8).
A novel isobenzofuranone derivative, pseudaboydins A (31) was isolated from the marine fungus, Pseudallescheria boydii, associated with the starfish, Acanthaster planci. Compound 31 showed A steroid derivative, compound 28 was isolated from the fermentation broth of a gorgonianderived Aspergillus sp. fungus. The fungus was isolated from the inner part of the fresh gorgonian M. abnormalis, which was collected from the Xisha Islands coral reef of the South China Sea. Compound 28 inhibited the larval settlement of barnacle Balanus amphitrite with EC 50 18.40˘2.0 µg/mL (Figure 7) [20].
A new diphenyl ether derivative, talaromycin A (29) was isolated from a gorgonian-derived fungus, Talaromyces sp. The fungal strain was isolated from a piece of fresh tissue from the inner part of the gorgonian Subergorgia suberosa, collected from the Weizhou coral reef in the South China Sea. Compound 29 showed potent antifouling activities against the larval settlement of the barnacle Balanus amphitrite with the EC 50 value 2.8˘0.2 µg/mL (Figure 7) [21].

Starfish
Liang et al. [22] investigated the influence on secondary metabolites with variety of cultivation parameters of marine fungus, Neosartorya pseudofischeri, which was isolated from the inner tissue of starfish Acanthaster planci. Glycerol-peptone-yeast extract (GlyPY) and glucose-peptone-yeast extract (GluPY) media were applied to culture this fungus. A novel gliotoxin (30) was produced with GluPY medium. Compound 30 displayed significant inhibitory activities against three multidrug-resistant bacteria, S. aureus (ATCC29213), MRSA (R3708) and Escherichia coli (E. coli) (ATCC25922), as well as cytotoxicities against some cell lines including human embryonic kidney (HEK) 293 cell line and human colon cancer cell lines, HCT-116 and RKO (a poorly differentiated colon carcinoma cell line) ( Figure 8).

Sea Urchin
The Penicillium sp. SF-6013 was isolated from the sea urchin Brisaster latifrons, which was collected from the Sea of Okhotsk. Chemical investigation of strain SF-6013 resulted in the discovery of a new tanzawaic acid derivative, 2E,4Z-tanzawaic acid D (38). Screening for anti-inflammatory effects in lipopolysaccharide (LPS)-activated microglial BV-2 cells indicated that compound 38 inhibited the production of nitric oxide (NO) with IC50 values of 37.8 μM ( Figure 10) [26].

Fish
Two new rubrolides, rubrolides R (39) and S (40), were isolated from the fermentation broth of the marine-derived fungus Aspergillus terreus OUCMDZ-1925, which was isolated from the viscera of C. haematocheilus grown in the waters of the Yellow River Delta. Compound 39 showed comparable or superior antioxidation against ABTS radicals to those of trolox and ascorbic acid with an IC50 value of 1.33 μM. Compound 40 showed comparable or superior anti-influenza A (H1N1)

Sea Urchin
The Penicillium sp. SF-6013 was isolated from the sea urchin Brisaster latifrons, which was collected from the Sea of Okhotsk. Chemical investigation of strain SF-6013 resulted in the discovery of a new tanzawaic acid derivative, 2E,4Z-tanzawaic acid D (38). Screening for anti-inflammatory effects in lipopolysaccharide (LPS)-activated microglial BV-2 cells indicated that compound 38 inhibited the production of nitric oxide (NO) with IC50 values of 37.8 μM ( Figure 10) [26].

Fish
Two new rubrolides, rubrolides R (39) and S (40), were isolated from the fermentation broth of the marine-derived fungus Aspergillus terreus OUCMDZ-1925, which was isolated from the viscera of C. haematocheilus grown in the waters of the Yellow River Delta. Compound 39 showed comparable or superior antioxidation against ABTS radicals to those of trolox and ascorbic acid with an IC50 value of 1.33 μM. Compound 40 showed comparable or superior anti-influenza A (H1N1)

Sea Urchin
The Penicillium sp. SF-6013 was isolated from the sea urchin Brisaster latifrons, which was collected from the Sea of Okhotsk. Chemical investigation of strain SF-6013 resulted in the discovery of a new tanzawaic acid derivative, 2E,4Z-tanzawaic acid D (38). Screening for anti-inflammatory effects in lipopolysaccharide (LPS)-activated microglial BV-2 cells indicated that compound 38 inhibited the production of nitric oxide (NO) with IC 50 values of 37.8 µM ( Figure 10) [26].

Fish
Two new rubrolides, rubrolides R (39) and S (40), were isolated from the fermentation broth of the marine-derived fungus Aspergillus terreus OUCMDZ-1925, which was isolated from the viscera of C. haematocheilus grown in the waters of the Yellow River Delta. Compound 39 showed comparable or superior antioxidation against ABTS radicals to those of trolox and ascorbic acid with an IC 50

Others
The marine-derived fungus Eurotium amstelodami was isolated from an unidentified marine animal collected from the Sungsan coast in Jeju Island, Korea. An anthraquinone derivative, questinol (43) was successfully isolated from the broth extract of the fungus for the first time. Questinol (43) did not exhibit cytotoxicity in LPS-stimulated RAW 264.7 cells up to 200 μM while could significantly inhibit NO and PGE2 production at indicated concentrations. Furthermore, it could inhibit the production of pro-inflammatory cytokines, including IL-1β, TNF-α, and IL-6 and suppress the expression level of iNOS in a dose-dependent manner through the western blot analysis. All these results suggest that questinol might be selected as a promising agent for the prevention and therapy of inflammatory disease ( Figure 11) [29].
A novel aspochalasin, 20-β-methylthio-aspochalsin Q (named as aspochalasin V, 44) was isolated from culture broth of Aspergillus sp., which was obtained in the gut of a marine isopod Ligia oceanica (Dinghai in Zhoushan, Zhejiang Province of China). This is the first report about methylthio-substituted aspochalasin derivative. Apochalasin V showed moderate cytotoxic activity against the prostate cancer PC3 cell line and HCT116 cell line with IC50 values of 30.4 and 39.2 μM, respectively ( Figure 11) [30].
Two new cerebrosides, penicillosides A (45) and B (46) were isolated from the marine-derived fungus Penicillium species, which were gained from the Red Sea tunicate, Didemnum species in the Mangrove. Penicilloside A displayed antifungal activity against Candida albicans while penicilloside B illustrated antibacterial activities against S. aureus and E. coli. Additionally, both compounds showed weak activity against HeLa cells ( Figure 11) [31].

Others
The marine-derived fungus Eurotium amstelodami was isolated from an unidentified marine animal collected from the Sungsan coast in Jeju Island, Korea. An anthraquinone derivative, questinol (43) was successfully isolated from the broth extract of the fungus for the first time. Questinol (43) did not exhibit cytotoxicity in LPS-stimulated RAW 264.7 cells up to 200 µM while could significantly inhibit NO and PGE 2 production at indicated concentrations. Furthermore, it could inhibit the production of pro-inflammatory cytokines, including IL-1β, TNF-α, and IL-6 and suppress the expression level of iNOS in a dose-dependent manner through the western blot analysis. All these results suggest that questinol might be selected as a promising agent for the prevention and therapy of inflammatory disease ( Figure 11) [29].
A novel aspochalasin, 20-β-methylthio-aspochalsin Q (named as aspochalasin V, 44) was isolated from culture broth of Aspergillus sp., which was obtained in the gut of a marine isopod Ligia oceanica (Dinghai in Zhoushan, Zhejiang Province of China). This is the first report about methylthio-substituted aspochalasin derivative. Apochalasin V showed moderate cytotoxic activity against the prostate cancer PC3 cell line and HCT116 cell line with IC 50 values of 30.4 and 39.2 µM, respectively ( Figure 11) [30].
Two new cerebrosides, penicillosides A (45) and B (46) were isolated from the marine-derived fungus Penicillium species, which were gained from the Red Sea tunicate, Didemnum species in the Mangrove. Penicilloside A displayed antifungal activity against Candida albicans while penicilloside B illustrated antibacterial activities against S. aureus and E. coli. Additionally, both compounds showed weak activity against HeLa cells ( Figure 11) [31].
A new alkaloid, brocaeloid B (55), containing C-2 reversed prenylation, was isolated from cultures of Penicillium brocae MA-192, an endophytic fungus obtained from the fresh leaves of the marine mangrove plant Avicennia marina in Hainan island, China. Compound 55 showed lethality against brine shrimp (Artemia salina) with an LD50 value of 36.7 μM ( Figure 13) [34].

Mangrove
Six new compounds with polyketide decalin ring, peaurantiogriseols A-F (47-52), were isolated from the fermentation products of mangrove endophytic fungus Penicillium aurantiogriseum328#, which was collected from the bark of Hibiscus tiliaceus in the Qi'ao Mangrove Aspergifuranone (53), isocoumarin derivatives (±) 54 were separated from the mangrove endophytic fungus Aspergillus sp. 16-5B, which was isolated from the leaves of Sonneratia apetala from Dongzhaigang Mangrove National Nature Reserve in Hainan Island, China. Both of them were evaluated for their α-glucosidase inhibitory activities, and compound 53 showed significant inhibitory activity with IC50 value of 9.05 ± 0.60 μM. Kinetic analysis showed that compound 53 was a noncompetitive inhibitor of α-glucosidase. Compound 54 exhibited moderate inhibitory activities, with IC50 value of 90.4 ± 2.9 μM ( Figure 13) [33].
A new alkaloid, brocaeloid B (55), containing C-2 reversed prenylation, was isolated from cultures of Penicillium brocae MA-192, an endophytic fungus obtained from the fresh leaves of the marine mangrove plant Avicennia marina in Hainan island, China. Compound 55 showed lethality against brine shrimp (Artemia salina) with an LD50 value of 36.7 μM ( Figure 13) [34].
A new alkaloid, brocaeloid B (55), containing C-2 reversed prenylation, was isolated from cultures of Penicillium brocae MA-192, an endophytic fungus obtained from the fresh leaves of the marine mangrove plant Avicennia marina in Hainan island, China. Compound 55 showed lethality against brine shrimp (Artemia salina) with an LD 50 value of 36.7 µM ( Figure 13) [34].
Four new disulfide-bridged diketopiperazine derivatives, brocazines (57-60) were isolated from Penicillium brocae MA-231, a fungus obtained from the fresh tissue of the marine mangrove plant Avicennia marina that was collected at Hainan Island, China. Compounds 57-60 showed cytotoxic activities against nine tumor cell lines, including Du145, HepG2, HeLa, NCI-H460, MCF-7, SGC-7901, SW1990, U251 and SW480, with IC 50 values ranging from 0.89 to 9.0 µM ( Figure 13) [36].   A new aromatic amine, pestalamine A (75) was isolated from mangrove-derived endophytic fungus Pestalotiopsis vaccinii that was isolated from a branch of Kandelia candel (L.) Druce (Rhizophoraceae), a usual viviparous mangrove species in coastal and estuarine areas of southern  A new aromatic amine, pestalamine A (75) was isolated from mangrove-derived endophytic fungus Pestalotiopsis vaccinii that was isolated from a branch of Kandelia candel (L.) Druce (Rhizophoraceae), a usual viviparous mangrove species in coastal and estuarine areas of southern
Two novel tetracyclic oxindole alkaloids, speradines G (93) and H (94), were isolated from the marine-derived fungus Aspergillus oryzae, isolated from marine sediments (Langqi Island, Fujian, China). This is the first report on cyclopiazonic acid (CPA)-type alkaloids with a hexacyclic skeleton. The compounds 93-94 showed unconspicuous cytotoxic effects on the Hela, HL-60 and K562 cell lines, IC50 values larger than 30 μg/mL ( Figure 21) [56].         Ascotricha sp. ZJ-M-5, is a fungus isolated from a mud sample, which was collected on a coastal beach in Fenghua County, Zhejiang Province, China. Chemical investigations were found to produce cyclonerodiol analogues, a 3,4-seco lanostane triterpenoid, and diketopiperazines in an eutrophic medium by the one strain-many compounds (OSMAC) analysis. Two new caryophyllene derivatives (113-114) were produced in an oligotrophic medium, Czapek Dox broth with or without Mg 2+ . (+)-6-O-Demethylpestalotiopsin A (113) and (+)-6-O-demethylpestalotiopsin C (114), which have a five-membered hemiacetal structural moiety, showed growth inhibitory abilities against K562 and HL-60 leukemia cell lines with the lowest GI 50 value of 6.9˘0.4 µM. This indicated that modification of the culture media was effective in the discovery of novel bioactive fungal secondary metabolites ( Figure 24) [63].
The marine fungus Cladosporium sp. was isolated from a sediment sample collected from Yangshashan Bay, Ningbo, Zhejiang Province, China. Two new sulfur-containing diketopiperazines (DKPs), cladosporin A (115) and cladosporin B (116), were separated from the fungus by high-speed counter-current chromatography (HSCCC). Cytotoxic activity tests showed that compounds 115 and 116 exhibited moderate cytotoxic activities to HepG2 cell line, with values of IC 50
Five new polyketides (122-126) have been isolated from the lipophilic extracts of the marine-derived fungi Penicillium thomii and Penicillium lividum isolated from superficial mycobiota of the brown alga Sargassum miyabei (Lazurnaya Bay, the Sea of Japan). Compound 123 was able to inhibit the transcriptional activity of the oncogenic nuclear factor AP-1 with IC50 value of 15 μM after 12 h of treatment. Compound 125 exhibited cytotoxicity against splenocytes with a IC50 value of 38 μM. It was shown that compounds 124 and 126 at a non-toxic concentration (10 μM) inhibited the adhesion of macrophages (30%-40% of inhibition). In addition, compounds 122 and 125 exhibited
Five new polyketides (122-126) have been isolated from the lipophilic extracts of the marine-derived fungi Penicillium thomii and Penicillium lividum isolated from superficial mycobiota of the brown alga Sargassum miyabei (Lazurnaya Bay, the Sea of Japan). Compound 123 was able to inhibit the transcriptional activity of the oncogenic nuclear factor AP-1 with IC50 value of 15 μM after 12 h of treatment. Compound 125 exhibited cytotoxicity against splenocytes with a IC50 value of 38 μM. It was shown that compounds 124 and 126 at a non-toxic concentration (10 μM) inhibited the adhesion of macrophages (30%-40% of inhibition). In addition, compounds 122 and 125 exhibited
Five new polyketides (122-126) have been isolated from the lipophilic extracts of the marine-derived fungi Penicillium thomii and Penicillium lividum isolated from superficial mycobiota of the brown alga Sargassum miyabei (Lazurnaya Bay, the Sea of Japan). Compound 123 was able to inhibit the transcriptional activity of the oncogenic nuclear factor AP-1 with IC 50 value of 15 µM after 12 h of treatment. Compound 125 exhibited cytotoxicity against splenocytes with a IC 50 value of 38 µM. It was shown that compounds 124 and 126 at a non-toxic concentration (10 µM) inhibited the adhesion of macrophages (30%-40% of inhibition). In addition, compounds 122 and 125 exhibited radical scavenging activity against DPPH with IC 50 values of 100 and 50 µM, respectively ( Figure 26) [68].   Figure 27. Structures of compounds 127-133.
The fungal strain Penicillium echinulatum pt-4 was isolated from marine red alga Chondrus ocellatus that was collected from the coast of Pingtan Island, China. One new meroterpene, arisugacin K (134) was isolated from the culture of strain pt-4. Compound 134 showed inhibitory activity against E. coli with an inhibition diameter 8 mm at 30 μg/disk ( Figure 28) [70].
The fungal strain Penicillium echinulatum pt-4 was isolated from marine red alga Chondrus ocellatus that was collected from the coast of Pingtan Island, China. One new meroterpene, arisugacin K (134) was isolated from the culture of strain pt-4. Compound 134 showed inhibitory activity against E. coli with an inhibition diameter 8 mm at 30 μg/disk ( Figure 28) [70].
A  The fungal strain Penicillium echinulatum pt-4 was isolated from marine red alga Chondrus ocellatus that was collected from the coast of Pingtan Island, China. One new meroterpene, arisugacin K (134) was isolated from the culture of strain pt-4. Compound 134 showed inhibitory activity against E. coli with an inhibition diameter 8 mm at 30 µg/disk ( Figure 28) [70].
The fungus Penicillium 303# was isolated from sea water, which was collected from Zhanjiang Mangrove National Nature Reserve in Guangdong Province, China. Three new metabolites (compounds 144-146) were isolated from the fungus fermentation medium. Those compounds showed weak to moderate cytotoxic activities against MDA-MB-435 ( Figure 31) [78].
The fungus Penicillium 303# was isolated from sea water, which was collected from Zhanjiang Mangrove National Nature Reserve in Guangdong Province, China. Three new metabolites (compounds 144-146) were isolated from the fungus fermentation medium. Those compounds showed weak to moderate cytotoxic activities against MDA-MB-435 ( Figure 31) [78]. A marine strain Stachybotrys sp. MF347, which was isolated from a driftwood sample collected at Helgoland (North Sea, Germany), provided a novel spirocyclic drimane coupled by two drimane fragment building blocks 147. Compound 147 exhibited comparable antibacterial activities with chloramphenicol against the clinically relevant MRSA (Figure 32) [79].
A strain of the fungus Penicillium chrysogenum was collected from sea water (10-25 m depth), off the North Sea coast, China. A new benzoic acid, 2-(2-hydroxypropanamido) benzoic acid (149), isolated from the fermentation broth of fungus, showed remarkable anti-inflammatory and analgesic activities but exhibited no ulcerogenic effect ( Figure 32) [81].
A strain of the fungus Penicillium chrysogenum was collected from sea water (10-25 m depth), off the North Sea coast, China. A new benzoic acid, 2-(2-hydroxypropanamido) benzoic acid (149), isolated from the fermentation broth of fungus, showed remarkable anti-inflammatory and analgesic activities but exhibited no ulcerogenic effect ( Figure 32) [81].
The fungus Penicillium 303# was isolated from sea water, which was collected from Zhanjiang Mangrove National Nature Reserve in Guangdong Province, China. Three new metabolites (compounds 144-146) were isolated from the fungus fermentation medium. Those compounds showed weak to moderate cytotoxic activities against MDA-MB-435 ( Figure 31) [78]. A marine strain Stachybotrys sp. MF347, which was isolated from a driftwood sample collected at Helgoland (North Sea, Germany), provided a novel spirocyclic drimane coupled by two drimane fragment building blocks 147. Compound 147 exhibited comparable antibacterial activities with chloramphenicol against the clinically relevant MRSA (Figure 32) [79].
A strain of the fungus Penicillium chrysogenum was collected from sea water (10-25 m depth), off the North Sea coast, China. A new benzoic acid, 2-(2-hydroxypropanamido) benzoic acid (149), isolated from the fermentation broth of fungus, showed remarkable anti-inflammatory and analgesic activities but exhibited no ulcerogenic effect ( Figure 32) [81].

Others
Racemic dinaphthalenone derivatives (˘)-asperlone A (150) and (˘)-asperlone B (151) were isolated from the cultures of Aspergillus sp. 16-5C from the leaves of S. apetala, which were collected in Hainan Island, China. Compounds 150 and 151 exhibited potent inhibitory effects against Mycobacterium tuberculosis protein tyrosine phosphatase B (MptpB) with IC 50 values of 4.24˘0.41, 4.32˘0.60 µM, respectively, which represent a new type of lead compounds for the development of new anti-tuberculosis drugs ( Figure 33) [82].
A new polychlorinated triphenyl diether named microsphaerol (152) and a new naphthalene derivative named seimatorone (153), were isolated from the endophtic fungus Microsphaeropsis sp. and Seimatosporium sp., which were isolated from the halotolerant herbaceous plant Salsola oppositifolia from Playa del Ingles (Gomera, Spain). Preliminary studies revealed that compound 152 showed good antibacterial activities against Bacillus Megaterium and E. coli, and good antilagal and antifungal activities against Chlorella fusca and Microbotryum violaceum, respectively. On the other hand, compound 153 exhibited moderate antibacterial, antialgal, and antifungal activities ( Figure 33) [83].

Future Perspectives and Concluding Remarks
Based on the above literature, we can find that marine-derived Aspergillus and Penicillium are the most ubiquitous genera, probably because both of them are salt tolerant, fast growing and easily obtained. As seen in Figure 34, about 3/4 of all new compounds reported from marine fungi are derived from isolation from living matter, i.e. marine animals (30.1%) and marine plants (42.5%), while the remaining compounds are obtained from non-living sources, most notably sediments (22.9%). Within the individual groups, mangrove habitats (25.5%), alga (14.4%), and sponges (9.2%) are the predominant sources for fungal diversity. A newly emerging source is the deep sea. The extreme environment encountered in the form of low temperature, elevated hydrostatic pressure, absence of light, high concentrations of metals in hydrothermal vents and hypoxic conditions possibly produce structurally unique metabolites. Nevertheless, very few reports are related to this habitat because of scarcity of source. It is worth mentioning that an increasing number of Chinese scientists are engaging in this research field, mostly focusing on mangrove areas around South China Sea.
As illustrated in Figure 36, biological activities of these compounds are mainly focused in the areas of cytotoxicity (37.5%) and antimicrobial activity, including antibacterial activity (18.4%), antifungal activity (7.9%) and antiviral activity (7.2%). Furthermore, other selective activities include antioxidant, anti-inflammatory, antifouling, lipid-lowering activities, lethality against brine shrimp effects, etc.
The oceans are the largest underexploited wealthy resource of potential drugs. Marine-derived fungi have provided a variety of potential pharmacological metabolites and thus represent a valuable resource of new drug candidates. In the period covered by the first review of this series, from the beginning until 2002, 272 new structures had been reported, in 2009 more than 200 was reached [2], and in 2012 and 2013, the numbers were 288 and 302, respectively [3,84]. Though bioactivities of secondary metabolites from marine fungi reveal interesting levels for a number of clinical relevant targets, they are not well represented in the pipelines of drugs and none of them currently is on the market. Only Plinabulin, a synthetic cyclic dipeptide analogue of halimide, which is isolated from a marine fungus species, is in phase II clinical trial for treatment of non-small

Future Perspectives and Concluding Remarks
Based on the above literature, we can find that marine-derived Aspergillus and Penicillium are the most ubiquitous genera, probably because both of them are salt tolerant, fast growing and easily obtained. As seen in Figure 34, about 3/4 of all new compounds reported from marine fungi are derived from isolation from living matter, i.e. marine animals (30.1%) and marine plants (42.5%), while the remaining compounds are obtained from non-living sources, most notably sediments (22.9%). Within the individual groups, mangrove habitats (25.5%), alga (14.4%), and sponges (9.2%) are the predominant sources for fungal diversity. A newly emerging source is the deep sea. The extreme environment encountered in the form of low temperature, elevated hydrostatic pressure, absence of light, high concentrations of metals in hydrothermal vents and hypoxic conditions possibly produce structurally unique metabolites. Nevertheless, very few reports are related to this habitat because of scarcity of source. It is worth mentioning that an increasing number of Chinese scientists are engaging in this research field, mostly focusing on mangrove areas around South China Sea.  According to the structural types, of the 153 compounds included in this review, alkaloids (27.0%) and polyketides (25.7%) play a dominant role. Moreover, peptides, terpenes, lactone, and steroids are 13.8%, 9.9%, 3.9% and 3.3%, respectively (see Figure 35).   First of all, many marine-derived fungal biosynthetic pathways are silent under common laboratory culture conditions, and activation of the silent pathways may enable access to new metabolites. One strain-many compounds (OSMAC) strategy, chemical epigenetic modification (e.g., using DNA methyltransferase inhibitor, 5-azacytidine, histone deacetylase inhibitors, suberoylanilide hydroxamic acid and sodium butyrate [60][61][62][86][87][88]), co-culture method [48], or gene level manipulations could be applied to access new secondary metabolites. Furthermore, as mentioned above, alterations of the culture conditions might lead to changes of the metabolic spectrum. The pharmaceutical industry should concentrate on how to appropriately maintain As illustrated in Figure 36, biological activities of these compounds are mainly focused in the areas of cytotoxicity (37.5%) and antimicrobial activity, including antibacterial activity (18.4%), antifungal activity (7.9%) and antiviral activity (7.2%). Furthermore, other selective activities include antioxidant, anti-inflammatory, antifouling, lipid-lowering activities, lethality against brine shrimp effects, etc.   First of all, many marine-derived fungal biosynthetic pathways are silent under common laboratory culture conditions, and activation of the silent pathways may enable access to new metabolites. One strain-many compounds (OSMAC) strategy, chemical epigenetic modification (e.g., using DNA methyltransferase inhibitor, 5-azacytidine, histone deacetylase inhibitors, suberoylanilide hydroxamic acid and sodium butyrate [60][61][62][86][87][88]), co-culture method [48], or gene level manipulations could be applied to access new secondary metabolites. Furthermore, as mentioned above, alterations of the culture conditions might lead to changes of the metabolic spectrum. The pharmaceutical industry should concentrate on how to appropriately maintain The oceans are the largest underexploited wealthy resource of potential drugs. Marine-derived fungi have provided a variety of potential pharmacological metabolites and thus represent a valuable resource of new drug candidates. In the period covered by the first review of this series, from the beginning until 2002, 272 new structures had been reported, in 2009 more than 200 was reached [2], and in 2012 and 2013, the numbers were 288 and 302, respectively [3,84]. Though bioactivities of secondary metabolites from marine fungi reveal interesting levels for a number of clinical relevant targets, they are not well represented in the pipelines of drugs and none of them currently is on the market. Only Plinabulin, a synthetic cyclic dipeptide analogue of halimide, which is isolated from a marine fungus species, is in phase II clinical trial for treatment of non-small cell lung cancer. Thus, there is still a long way to go [85].
First of all, many marine-derived fungal biosynthetic pathways are silent under common laboratory culture conditions, and activation of the silent pathways may enable access to new metabolites. One strain-many compounds (OSMAC) strategy, chemical epigenetic modification (e.g., using DNA methyltransferase inhibitor, 5-azacytidine, histone deacetylase inhibitors, suberoylanilide hydroxamic acid and sodium butyrate [60][61][62][86][87][88]), co-culture method [48], or gene level manipulations could be applied to access new secondary metabolites. Furthermore, as mentioned above, alterations of the culture conditions might lead to changes of the metabolic spectrum. The pharmaceutical industry should concentrate on how to appropriately maintain certain physico-chemical factors, viz., amount of oxygen available, optimum pH and temperature, avoiding variation of secondary metabolites.
What is more, a better understanding of the molecular basis of biosynthesis and regulation mechanisms will contribute to making better use of the enormous chemical potential of marine derived fungi, which depends on the continuous development of the new techniques [89,90].
In addition, beyond the current in vitro bioactivity examination, further in vivo and preclinical studies, as well as side effects examinations, are required to determine the bioactive compounds with potential therapeutic applications.
We believe that with the development of more automated and more affordable techniques for isolating and characterizing marine fungi bioactive metabolites, marine fungi will be promising sources for novel therapeutic agents that will be useful in controlling human diseases and protecting human health.