A new lanostane-type triterpenoid from the marine shellfish symbiotic fungus Ceriporia lacerata CD7-5

One new lanostane-type triterpenoid, 3β-acetoxy-7,11-dioxolanosta-8,24-dien-21-oic acid (1), together with six known analogues (2-7), were isolated from the cultures of a marine fungus Ceriporia lacerata CD7-5, which was derived from the shellfish Ostrea denselamellosa. Their structures were determined by detailed analysis of spectroscopic data and comparison with the literature reported. The biological activities of these lanostane triterpenoids against marine-derived microalgae, zooplankton, and pathogenic bacteria were also evaluated in this study.

A new secondary metabolite from the marine-derived fungus Phomopsis lithocarpus FS508

Based on the One Strain-Many Compounds (OSMAC) strategy, the secondary metabolites of Phomopsis lithocarpus FS508 were investigated. As a result, a new secondary metabolite, 4-methoxy-3-[4-(acetyloxy)-3-methyl-2-butenyl]benzoic acid (1) as well as eleven known compounds were isolated from the fermentation product of the strain FS508. Their structures were determined by NMR, IR, UV, and MS spectroscopic data analyses. All the isolated compounds were evaluated for cytotoxic and anti-inflammatory activities. Among them, compounds 3 and 9 displayed potent cytotoxicity against HepG-2 cell line, and compounds 2, 3 and 12 showed significant anti-inflammatory activities.

Discovery of a novel anti-osteoporotic agent from marine fungus-derived structurally diverse sirenins

Thirteen new sirenin derivatives named eupenicisirenins C-O (1-13), along with a biosynthetically related known one (14), were isolated from the mangrove sediment-derived fungus Penicillium sp. SCSIO 41410. The structures, which possessed a rare cyclopropane moiety, were confirmed by extensive analyses of the spectroscopic data, quantum chemical calculations, and X-ray diffraction. Among them, eupenicisirenin C (1) exhibited the strongest NF-κB inhibitory activities, as well as suppressing effects on cGAS-STING pathway. Moreover, 1 showed the significant inhibitory effect on RANKL-induced osteoclast differentiation in bone marrow macrophages cells, and also displayed the therapeutic potential on prednisolone-induced zebrafish osteoporosis. Transcriptome analysis and the following verification tests suggested that its anti-osteoporotic mechanism is related to the extracellular matrix receptor interaction-related pathways. This study provided a promising marine-derived anti-osteoporotic agent for the treatment of skeletal disease.

Aspertaichamide a, a novel cytotoxic prenylated indole alkaloid possessing a bicyclo[2.2.2]diazaoctane framework from a marine algal-derived endophytic fungus aspergillus taichungensis 299

Filamentous fungi belonging to the genus Aspergillus are prodigious producers of alkaloids, particularly prenylated indole alkaloids, that often exhibit structurally diversified skeletons and potent biological activities. In this study, five prenylated indole alkaloids possessing a bicyclo[2.2.2]diazaoctane core ring system, including a novel derivative, namely aspertaichamide A (1), as well as four known compounds, (+)-stephacidin A (2), sclerotiamide (3), (-)-versicolamide B (4), and (+)-versicolamide B (5), were isolated and identified from A. taichungensis 299, an endophytic fungus obtained from the marine red alga Gelidium amansii. The chemical structures of the compounds were elucidated by comprehensive NMR and HRESIMS spectroscopic analyses. In addition to the previously reported prenylated indole alkaloids, aspertaichamide A (1) was characterized as having an unusual ring structure with the fusion of a 3-pyrrolidone dimethylbenzopyran to the bicyclo[2.2.2]diazaoctane moiety, which was rare in these kinds of compounds. The absolute configuration of 1 was determined by TDDFT-ECD calculations. In vitro cytotoxic assays revealed that the novel compound 1 possessed selective cytotoxic activity against five human tumor cell lines (A549, HeLa, HepG2, HCT-116, and AGS), with IC50 values of 1.7-48.5 μM. Most importantly, compound 1 decreased the viability of AGS cells in a concentration-dependent manner with an IC50 value of 1.7 μM. Further studies indicated that 1 may induce AGS cells programmed cell death via the apoptotic pathway.

New ophiobolin sesterterpenoid and drimane sesquiterpenoids from a marine-alga-derived fungus Aspergillus sp

Further investigation of secondary metabolites of a marine-alga-derived fungus Aspergillus sp. RR-YLW-12 led to isolate one new ophiobolin-type sesterterpenoid (1), four new drimane-type sesquiterpenoids (2-5) and one natural occurring compound (6), together with seven known compounds (7-13). Their structures and stereochemistry were elucidated by extensive spectroscopic analysis of NMR and HRMS experiments, and by comparison with the literature data. All isolates were evaluated for growth inhibition of five marine harmful microalgae. The new compounds exhibited significant to moderate inhibitory effects towards all tested microalgae species with IC50 values ranging from 5.8 to 54.5 μg/mL.

Myrochromanol analogues and trichothecene derivatives from the shellfish-derived fungus Albifimbriaverrucaria

Eight myrochromanol analogues, including three pairs of epimers at C-2 with the myrochromanol scaffold and two examples of myrochromanol with sugar moiety linked at C-4, together with twelve trichothecene derivatives were isolated from the cultures of a shellfish-derived fungus Albifimbria verrucaria CD1-4. Among them, eight compounds named 2-epi-myrochromanol, ent-myrochromanol B, 4-epi-myrochromanol B, 2-epi-myrochromanol A, myrochromanosides A and B, 6',7'-erythro-(2'E,4'Z)-trichoverrol B, 3R,8S-dihyroxyroridin H were previously undescribed fungal metabolites. Their planar structures and relative configurations were established by 1D and 2D NMR, and HR-MS data analysis, and their absolute configurations were determined using the modified Mosher's method and electronic circular dichrosim calculations. Almost all isolates were evaluated for growth rate inhibition of three marine harmful microalgae Chattonella marina, Heterosigma akashiwo, and Prorocentrum donghaiense, and lethal activity to one marine zooplankton, Artemia salina. Myrochromanosides A and B exhibited obvious inhibitory against three tested microalgae with IC₅₀ values in the range of 9.2-108.9 μM. 8α-Hydroxyroridin H, roridin A and verrucarin A exhibited significant inhibition against P. donghaiense with IC₅₀ values of 6.1, 5.8, and 6.0 μM and toxicity against brine shrimp larvae with LC₅₀ values of 1.4, 2.8, and 0.26 μM, respectively.

Alterbutenolide, a new butenolide derivative from a sponge-derived fungus Alternaria alternata I-YLW6-1

Alterbutenolide (1), a new butenolide derivative with a long-chain aliphatic acid substitution, together with seven known phenolic compounds i.e. alternariol (2), asperigillol B (3), p-hydroxyphenylacetic acid (4), p-hydroxyphenylethyl alcohol (5), methyl p-hydroxyphenyl acetate (6), 2-(4-hydroxyphenyl)ethyl acetate (7), and 5,6-dihydro-4-methyl-2H-pyran-2-one (8), was isolated from the cultures of a sponge-derived fungus Alternaria alternata I-YLW6-1. The structure of 1 was established on the basis of HR-MS, 1D and 2D NMR, as well as by comparison of the optical rotation data with the literature reported. Compounds 2 and 3 showed significant to moderate inhibitory activities against three harmful microalgae with IC50 values from 3.0 to 36.2 μg/mL, whereas compound 1 only displayed moderate inhibition against Chattonella marina with IC50 value of 34.6 μg/mL. Meanwhile, compounds 3 and 4 showed weak toxicity against brine shrimp larvae with LC50 values >100 μg/mL.

Indole alkaloids fusarindoles A-E from marine-derived fungus Fusarium equiseti LJ-1

Five undescribed indole alkaloids, fusarindoles A-E, together with seven known compounds were obtained from the marine-derived fungus Fusarium equiseti LJ-1. Their chemical structures and absolute configurations were determined by comprehensive analysis of the NMR, HRMS, UV, IR, ECD calculation and single-crystal X-ray diffraction data. The possible biosynthetic pathways of fusarindoles C-E were proposed. The cytotoxicities of eleven compounds, including fusarindoles A-E and six known compounds, against five human cancer cell lines A549, CNE2, SUNE1, HepG2 and QGY7701 were evaluated.

Antimicrobial metabolites from the Indonesian mangrove sediment-derived fungus Penicillium chrysogenum sp. ZZ1151

A total of 14 compounds including a novel tetrasubstituted benzene derivative peniprenylphenol A were isolated from a scaled-up culture of the Indonesian mangrove sediment-derived fungus Penicillium chrysogenum ZZ1151 in rice medium. Structures of the isolated compounds were determined based on their NMR spectroscopic analyses, HRESIMS data, optical rotation calculations and comparison with the reported data. New peniprenylphenol A (1) was found to have antimicrobial activities against human pathogenic methicillin-resistant Staphylococcus aureus (MRSA), Escherichia coli and Candida albicans with MIC values of 6, 13, and 13 µg/mL, respectively. The known compounds of penicimumide (2), preparaherquamide (5), uridine (6), thymine (7), 1,2-seco-trypacidin (8) communol G (9), clavatol (10), 4-hydroxybenzeneacetic acid methyl ester (11), 2,5-dihydroxyphenylacetic acid methyl ester (12), 2-hydroxyphenylacetic acid methyl ester (13) and 4-hydroxyphenylethanone (14) showed antimicrobial activity against at least one of the three tested pathogens with MIC values of 3-25 µg/mL.

Phomaligols F-I, polyoxygenated cyclohexenone derivatives from marine-derived fungus Aspergillus flavus BB1

By tracing the ¹³C NMR resonances for carbonyls and enols, four new oxidized phomaligol derivatives, phomaligols F-I (1-4), along with seven known compounds (5-11) were isolated from the culture of the fungus Aspergillus flavus BB1 isolated from the marine shellfish Meretrix meretrix collected on Hailing Island, Yangjiang, China. The chemical structures and the absolute configurations of the new compounds were elucidated by MS, NMR, ECD, optical rotation, and ¹³C NMR calculations. Compounds 1 and 2 represent the first examples of phomaligol derivatives that contain an unusual bicyclic skeleton. All isolated compounds were tested for their cytotoxic activity. Among them, sporogen-AO 1 (8) showed potent inhibitory activity against the cancer cell lines A549, H1299, SK-BR-3, and HCT116 with IC₅₀ values of 0.13, 0.78, 1.19, and 1.32 μM, respectively. Phomaligol G (2) displayed cytotoxic activity against the A549 and H1299 cell lines with IC₅₀ values of 46.86 and 51.87 μM respectively. Additionally, phomaligol H (3) demonstrated cytotoxic activity against the A549 cell line with an IC₅₀ value of 65.53 μM. Mechanistic studies of compound 8 showed that it induced apoptosis of HCT116 cells in a dose-dependent manner.

Arthriniumsteroids A-D, four new steroids from the soft coral-derived fungus Simplicillium lanosoniveum SCSIO41212

Four new steroids derivatives, namely arthriniumsteroids A - D (1-4), together with two known compounds, were isolated from the soft coral-derived fungus Simplicillium lanosoniveum SCSIO41212. Their structures were elucidated by spectroscopic analysis and by comparison with those reported in the literature. The absolute configuration of 2 was confirmed by single-crystal X-ray diffraction. In bioassay, all compounds showed weak inhibitory activities against lipopolysaccharide (LPS)-induced nitric oxide (NO) production in RAW 264.7 cells.

Monascuslactams A-D, cytotoxic γ-lactams from marine fungus Monascus albidus BB3

Amino acid-directed strategy becomes an efficient way to explore the alkaloids' biosynthetic potential of marine fungi. The metabolites of marine fungus Monascus albidus BB3 were regulated obviously when cultured in GPY medium supplemented with L-tryptophan, L-phenylalanine, D,L-methionine, L-threonine, L-lysine, L-serine and L-valine. Four new γ-lactams, monascuslactams A-D (1-4), together with two known compounds pulchellalactam (5) and O-acetylperlolyrine (6) were obtained. Their structures were determined by comprehensive analysis on the 1 D and 2 D NMR, HRESIMS, UV and IR data, and their absolute configurations were assigned by the experimental and calculated ECD data analysis. Compounds 3, 4 and 6 showed moderate cytotoxicity against human cancer cell lines SUNE1, HepG2, QGY7701, GLC82, HCT116 and MDA-MB-231.

Preparation and uranium (VI) biosorption for tri-amidoxime modified marine fungus material

The preparation, characterization, and uranium (VI) adsorption properties of tri-amidoxime modified marine fungus material (ZZF51-GPTS-EDA-AM/ZGEA) were investigated in this study. ZGEA was synthesized by four steps of condensation, nucleophilic substitution, electrophilic addition, and nitrile amidoxime and characterized by a series of methods containing FT-IR, TGA, SEM, and BET. Contrasted with uranium (VI) adsorption capacity of original fungus mycelium (15.46 mg g^-1) that of the functional material (584.60 mg g^-1) was great under the optimal factors such as uranium (VI) ion concentration 40 mg L^-1, solid-liquid ratio 50 mg L^-1, pH of solution 5.5, and reaction time 120 min. The above data were obtained by the orthogonal method. The cyclic tests showed that ZGEA had good regeneration performance, and it could be recycled at least five adsorption-desorption processes. The thermodynamic experimental adsorption result fitted Langmuir and Freundlich models, which explored monolayer and double layers of uranium (VI) adsorption mechanism, and the kinetic adsorption results were in better consistent with the pseudo-second-order and pseudo-first-order dynamic models (R² > 0.999).

Four new steroids from the marine soft coral-derived fungus Penicillium sp. SCSIO41201

Penicildiones A-D (1-4), four new steroids derivatives together with three known compounds including 16α-methylpregna-17α,19-dihydroxy-(9,11)-epoxy-4-ene-3,18-dione-20-acetoxy (5), stachybotrylactone B (6) and stachybotrin (7) were isolated from the soft coral-derived fungus Penicillium sp. SCSIO41201, cultured in the 1% NaCl PDB substrate. Their structures were determined through spectroscopic methods and X-ray crystallography. Biological evaluation results revealed that 6 exhibited significant cytotoxic activity against HL-60, K562, MOLT-4, ACHN, 786-O, and OS-RC-2 cell lines with IC₅₀ values of 5.23, 4.12, 4.31, 23.55, 7.65 and 10.81 μmol·L^-1, respectively, while other compounds showed weak or no cytotoxicity at 50 μmol·L^-1.

Newly reported alkaloids produced by marine-derived Penicillium species (covering 2014-2018)

Alkaloids, especially heterocyclic alkaloids, have received remarkable attention due to their intriguing structures and potential pharmacological activities. The marine fungi residing in extreme environmental conditions are among the richest sources of these basic nitrogen-containing compounds. Fungal species belonging to the genus Penicillium have been studied worldwide for their biosynthetic potential for generating bioactive alkaloids. This paper offers a systematic review of the newly reported alkaloids produced by marine-derived Penicillium species over the past five years (covering the literature from the beginning of 2014 through the end of 2018) and describes the structural diversity, biological activities, and plausible biosynthetic pathway of the reported compounds. A total of 106 alkaloids and 81 references are included in this review, which is expected to be beneficial for drug development and biosynthesis in the near future.

Peniciphenalenins A-F from the culture of a marine-associated fungus Penicillium sp. ZZ901

Marine-derived fungi of the genus Penicillium represent a huge potential for synthesizing the secondary metabolites with structural and bioactive uniqueness and diversity. In this study, six previously undescribed compounds peniciphenalenins A-F and four known compounds (+)-sclerodin, (+)-scleroderolide, (+)-sclerodione, and physcion were isolated from the culture of a marine-derived fungus Penicillium sp. ZZ901. Structures of the isolated compounds were elucidated by a combination of extensive NMR spectroscopic analysis, HRESIMS data, optical rotation value, ECD calculation, and single crystal X-ray diffraction. Peniciphenalenins A-C are the second examples of the type of neoherqueinones. The possible biosynthetic route of nine phenalenone derivatives has been suggested. The known (+)-scleroderolide showed both antiproliferative activity against glioma cells with IC₅₀ values of 23.24-37.26 μM and antibacterial activity in suppressing the growth of methicillin-resistant Staphylococcus aureus and Escherichia coli with MIC values of 7.0 and 9.0 μg/mL, respectively.

New metabolites from the sponge-derived fungus Aspergillus sydowii J05B-7F-4

Two new metabolites, diorcinolic acid (1) and β-d-glucopyranosyl aspergillusene A (8), together with six diphenylethers (2-7), a diketopiperazine (9), a chromone (10) and a xanthone (11) were isolated from the fungus Aspergillus sydowii derived from the marine sponge Stelletta sp. The planar structures and their relative configurations were elucidated by analysing 1D, 2D NMR and HRESIMS data. Compound 8 is the first glycoside of phenolic bisabolane sesquiterpenes. Compounds 1 and 8 exhibited mild cytotoxicity against KB (human nasopharyngeal carcinoma cells), HepG2 (human liver cancer cells) and HCT 116 (human colon cancer cells). All compounds were evaluated for antibacterial activity and their abilities to suppress LPS-induced nitric oxide (NO) production. Compounds 2 and 4-7 showed mild antibacterial activity against human pathogen Staphylococcus aureus and fish pathogens Streptococcus iniae and Vibrio ichthyoenteri, and compounds 4 and 7 weakly suppressed NO production.

Apoptotic effect of demethoxyfumitremorgin C from marine fungus Aspergillus fumigatus on PC3 human prostate cancer cells

Demethoxyfumitremorgin C, a secondary metabolite of the marine fungus, Aspergillus fumigatus, had been reported to demonstrate cytotoxic effect on mouse tsFT210 cells. However, no information is available regarding its functional mechanism and the chemo-sensitization effects on different kinds of human cancer cells. We found that treatment of demethoxyfumitremorgin C inhibited the cell viability of PC3 human advanced prostate cancer cells, induced apoptosis as determined by Annexin V/propidium iodide double staining, and decreased mitochondrial membrane potential. Demethoxyfumitremorgin C induced apoptosis was associated with downregulation of anti-apoptotic proteins: Ras, PI3K, Akt, Bcl-xL, and Bcl-2, and upregulation of pro-apoptotic Bax. Demethoxyfumitremorgin C activated caspase-3, -8, and -9, leading to PARP cleavage. Additionally, caspase inhibitors blocked demethoxyfumitremorgin C-induced apoptosis of PC3 cells. These results suggest that demethoxyfumitremorgin C from Aspergillus fumigatus inhibits the proliferation of PC3 human prostate cancer cells via the intrinsic (mitochondrial) and extrinsic pathway, followed by downstream events leading to apoptotic cell death. Demethoxyfumitremorgin C could therefore, serve as a useful agent to treat human advanced prostate cancer.

New metabolites from the sponge-derived fungus Aspergillus sydowii J05B-7F-4

Two new metabolites, diorcinolic acid (1) and β-d-glucopyranosyl aspergillusene A (8), together with six diphenylethers (2-7), a diketopiperazine (9), a chromone (10) and a xanthone (11) were isolated from the fungus Aspergillus sydowii derived from the marine sponge Stelletta sp. The planar structures and their relative configurations were elucidated by analysing 1D, 2D NMR and HRESIMS data. Compound 8 is the first glycoside of phenolic bisabolane sesquiterpenes. Compounds 1 and 8 exhibited mild cytotoxicity against KB (human nasopharyngeal carcinoma cells), HepG2 (human liver cancer cells) and HCT 116 (human colon cancer cells). All compounds were evaluated for antibacterial activity and their abilities to suppress LPS-induced nitric oxide (NO) production. Compounds 2 and 4-7 showed mild antibacterial activity against human pathogen Staphylococcus aureus and fish pathogens Streptococcus iniae and Vibrio ichthyoenteri, and compounds 4 and 7 weakly suppressed NO production.

A study on biological activity of marine fungi from different habitats in coastal regions

In recent years, marine fungi have become an important source of active marine natural products. Former researches are limited in habitats selection of fungi with bioactive compounds. In this paper were to measure antibacterial and antitumor cell activity for secondary metabolites of marine fungi, which were isolated from different habitats in coastal regions. 195 strains of marine fungi were isolated and purified from three different habitats. They biologically active experiment results showed that fungi isolation from the mangrove habitats had stronger antibacterial activity than others, and the stains isolated from the estuarial habitats had the least antibacterial activity. However, the strains separated from beach habitats strongly inhibited tumor cell proliferation in vitro, and fungi of mangrove forest habitats had the weakest activity of inhibiting tumor. Meanwhile, 195 fungal strains belonged to 46 families, 84 genera, 142 species and also showed 137 different types of activity combinations by analyzing the inhibitory activity of the metabolites fungi for 4 strains of pathogenic bacteria and B-16 cells. The study investigated the biological activity of marine fungi isolated from different habitats in Haikou coastal regions. The results help us to understand bioactive metabolites of marine fungi from different habitats, and how to selected biological activity fungi from various marine habitats effectively.

Perangustols A and B, a pair of new azaphilone epimers from a marine sediment-derived fungus Cladosporium perangustm FS62

A pair of new azaphilone epimers, perangustols A-B (1-2), and two new natural products (3-4), together with two known metabolites (5-6) were isolated from the culture of the marine sediment-derived fungus Cladosporium perangustum FS62. The structures of these compounds were established on the basis of extensive spectroscopic analysis. The isolated compounds (1-6) were evaluated for their cytotoxic activities against the SF-268, MCF-7, NCI-H460, and HepG-2 tumor cell lines. Nonetheless, no significant activity was observed.

Penicilazaphilone C, a new antineoplastic and antibacterial azaphilone from the Marine Fungus Penicillium sclerotiorum

Two azaphilonidal derivatives [penicilazaphilones B (1) and C (2)], have been isolated from the fermented products of marine fungus strain Penicillium sclerotiorum M-22, penicilazaphilones C was a new compound. The compound's structures were identified by the analysis of spectroscopic data including 1D and 2D NMR techniques (¹H-NMR, ¹³C-NMR, COSY, HMQC, and HMBC). Biological evaluation revealed that penicilazaphilones B and C showed selective cytotoxicity against melanoma cells B-16 and human gastric cancer cells SGC-7901 with IC₅₀ values of 0.291, 0.449 and 0.065, 0.720 mM, respectively, while exhibiting no significant toxicity to normal mammary epithelial cells M10 at the same concentration. Moreover, penicilazaphilones C also exhibited strong antibacterial activity against Staphylococcus aureus, Pseudomonas aeruginosa, Klebsiella pneumonia and Escherichia coli with MIC values 0.037-0.150 mM, while penicilazaphilones B's bacteriostatic action was weaker.

DNA Methyltransferase Inhibitor Induced Fungal Biosynthetic Products: Diethylene Glycol Phthalate Ester Oligomers from the Marine-Derived Fungus Cochliobolus lunatus

Chemical epigenetic manipulation was applied to the marine-derived fungus Cochliobolus lunatus (TA26-46) with a DNA methyltransferase inhibitor resulting in the significant changes of the secondary metabolites. Cultivation of C. lunatus (TA26-46) with 5-azacytidine led to the isolation of seven new diethylene glycol phthalate esters, cochphthesters A-G (1-6, 10), along with four known analogues (7-9, 11). Their structures were determined by extensive NMR spectroscopic spectra as well as MS data. Compounds 2-6 and 8-11, characterized by the cross-polymerization of phthalate across diethylene glycol via ester bonds, represent the first example of naturally occurring phthalate ester oligomers. Graphical Abstract Chemical epigenetic manipulation was applied to a marine-derived fungus resulting in significant changes of secondary metabolites.

Phenalenone derivatives and the unusual tricyclic sesterterpene acid from the marine fungus Lophiostoma bipolare BCC25910

Ten compounds including nine phenalenone derivatives (five bipolarides and four bipolarols) and a sesterterpene acid (bipolarenic acid), were isolated from a marine isolated of the fungus Lophiostoma bipolare (BCC25910), along with the known compounds, (-)-scleroderolide, (-)-sclerodin, and oxasetin. Chemical structures were elucidated based on NMR spectroscopic data and HRESIMS analysis. In addition, the absolute configurations of the phenalenones were resolved using specific rotations and chemical means, while the relative configuration of bipolarenic acid was confirmed by X-ray crystallographic analysis. The compounds were evaluated for biological activity against the Plasmodium falciparum K-1 strain, Candida albicans, and Bacillus cereus, and for cytotoxicity against both cancerous and non-cancerous cells.

Antibacterial activity of diketopiperazines isolated from a marine fungus using t-butoxycarbonyl group as a simple tool for purification

Nine diketopiperazines were characterized from the culture of marine fungal isolate MR2012 which based on DNA amplification and sequencing of the fungal internal transcribed spacer (ITS) region was identified as Aspergillus fumigatus. The isolated fungal metabolites 4-12 were unambiguously identified as a series of simple and re-arranged diketopiperazines by analysis of spectroscopic data. t-Butoxycarbonyl group (BOC) derivatization was used to separate the intractable mixture of 4 and 5. When all compounds were evaluated for antimicrobial activity against gram positive bacteria, the isolated metabolites showed moderate to weak effects, while the semisynthetic derivatives 4a and 5a displayed strong activity comparable to the positive control, tetracycline against gram positive bacteria.