Serpulanines A to C, N-Oxidized Tyrosine Derivatives Isolated from the Sri Lankan Fungus Serpula sp.: Structure Elucidation, Synthesis, and Histone Deacetylase Inhibition.

Serpulanines A (1), B (2), and C (3) have been isolated from extracts of the rare Sri Lankan macrofungus Serpula sp. The structures of 1, 2, and 3 were elucidated by a combination of spectroscopic and single-crystal X-ray diffraction analyses. Serpulanines A (1) and B (2) both contain the rare (E)-2-hydroxyimino hydroxamic acid functional group array. A proposed biogenesis for serpulanine B (2) suggests that its (E)-2-hydroxyimino hydroxamic acid moiety arises from a diketopiperazine precursor. Synthetic serpulanine A (1) inhibited class I/II histone deacetylases in murine metastatic lung carcinoma cells with an IC50 of 7 µM.

Antimicrobial activities of endophytic fungi of the Sri Lankan aquatic plant Nymphaea nouchali and chaetoglobosin A and C, produced by the endophytic fungus Chaetomium globosum.

Twenty distinct endophytic fungi were isolated from the surface-sterilized plant parts of Nymphaea nouchali and were identified using morphological and molecular techniques. At 300 µg/disc concentration, eight of the 20 fungal extracts exhibited antimicrobial activities against Staphylococcus aureus (ATCC 25923) and Bacillus cereus (ATCC 11778) while two within the eight showed activity against Pseudomonas aeruginosa (ATCC 9027) and Escherichia coli (ATCC 35218). Furthermore, investigation of the crude extract of Chaetomium globosum resulted in the isolation of two known cytochalasans, chaetoglobosin A and C, and their structures were elucidated and confirmed by mass and nuclear magnetic resonance (NMR) (1H, 13C, COSY, HSQC, HMBC and tROESY) spectral data. Chaetoglobosin A showed antibacterial activities against Bacillus subtilis (MIC 16 µg mL-1), Staphylococcus aureus (MIC 32 µg mL-1) and methicillin-resistant Staphylococcus aureus (MRSA, MIC 32 µg mL-1). This is the first study to report the isolation, identification and antimicrobial properties of endophytic fungi of N. nouchali in Sri Lanka.

Antioxidant potential, in vitro cytotoxicity and apoptotic effect induced by crude organic extract of Anthracophyllum lateritium against RD sarcoma cells.

BACKGROUND: Macrofungi have an established history of use in traditional oriental medicine. Anthracophyllum lateritium is a terrestrial macrofungus found in the dry zone forest reserves in Sri Lanka. Yet there are no scientific reports on bioactive properties of this species. Hence, the current study was aimed at determining the antioxidant potential, in vitro antiproliferative activity and apoptotic effect induced by crude methanolic extract of A. lateritium against RD sarcoma cell line. METHOD: The crude extract of A. lateritium was dissolved in methanol (MEFCA) and antioxidant activity was evaluated using in vitro assays: inhibition of DPPH (1,1-diphenyl-2-picrylhydrazyl) radical scavenging, ferric ion reducing power and 2-deoxy-D-ribose degradation assay. Total phenol and flavonoid contents of MEFCA were assayed using folin Ciocalteu method and aluminium chloride colorimetric method. In vitro cytotoxicity was determined using MTT assay against RD cells after 24 h exposure to MEFCA. Ethidium bromide/ acridine orange staining, DNA fragmentation and protein synthesis experiments were used to study the apoptotic features and antiproliferative activities of the treated cells. Glutathione assay and griess nitrite assay were used to analyze the reduced glutathione content and liberation of nitric oxide from apoptotic cells. RESULTS: MEFCA showed promising antioxidant activity with EC50 values of 8.00 ± 0.35 µg/mL for DPPH scavenging and 83.33 ± 0.45 µg/mL for 2-deoxy-D-ribose degradation assay. The phenolic content was 265.15 ± 0.46 of (w/w) % of Gallic acid equivalents and flavonoid content was 173.01 ± 0.35 of (w/w) % of Epigallocatechingallate. A. lateritium showed strong in vitro cytotoxic activity with an EC50 of 18.80 ± 4.83 µg/mL for MTT assay against RD cells. Ethidium bromide/acridine orange staining and DNA fragmentation indicated the apoptotic features of treated cells. Protein levels showed a dose dependent decrease supporting the fact that A. lateritium induces apoptosis of treated cells. Glutathione content and nitric oxide content of cells exhibited a dose dependent increase suggesting the apoptosis of RD cells was mediated by both nitrie ions and nitric oxide. CONCLUSIONS: The crude extract of the A. lateritium exhibited potent antioxidant, antiproliferative activity and apoptotic effect against RD cells providing supportive evidence for the ethnopharmacological use of this fungus in control of oxidative damage and remedy of cancer.

Helvolic acid, an antibacterial nortriterpenoid from a fungal endophyte, Xylaria sp. of orchid Anoectochilus setaceus endemic to Sri Lanka.

An endophytic fungus was isolated from surface sterilized leaf segments of Anoectochilus setaceus, an orchid endemic to Sri Lanka, and was identified as Xylaria sp. by morphological characters and DNA sequencing. Bioassay-guided chromatographic fractionation of the organic extract of a laboratory culture of this fungus led to the isolation of the known antibacterial helvolic acid. Helvolic acid was active against the Gram-positive bacteria, Bacillus subtilis [minimal inhibitory concentrations (MIC), 2 µg mL-1] and methicillin-resistant Staphylococcus aureus (MIC, 4 µg mL-1).

Dhilirolides A-D, meroterpenoids produced in culture by the fruit-infecting fungus Penicillium purpurogenum collected in Sri Lanka.

Dhilirolides A (1) to D (4), a family of secondary metabolites with a putative meroterpenoid biogenetic origin and the unprecedented dhilirane and isodhilirane carbon skeletons, have been isolated from laboratory cultures of the fruit-infecting fungus Penicillium purpurogenum collected in Sri Lanka. The structures of 1 to 4 were elucidated by interpretation of NMR data and a single crystal X-ray diffraction analysis of 1.

Lanostane triterpenoids from the Sri Lankan basidiomycete Ganoderma applanatum.

Two new lanostane-type triterpenoids, 3alpha,16alpha-dihydroxylanosta-7,9(11),24-trien-21-oic acid (1) and 3alpha,16alpha,26-trihydroxylanosta-7,9(11),24-trien-21-oic acid (2), along with three known lanostanoids, 16alpha-hydroxy-3-oxolanosta-7,9(11),24-trien-21-oic acid (3), 3alpha-carboxyacetoxy-24-methylen-23-oxolanost-8-en-26-oic acid (4), and 3alpha-carboxyacetoxy-24-methyl-23-oxolanost-8-en-26-oic acid (5), have been isolated from the EtOAc extract of the fruiting body of Ganoderma applanatum. The structures of 1, 2, and 3 were determined directly by the interpretation of spectroscopic data, while the structures of 4 and 5 were assigned by comparison of spectroscopic data against literature values.

Development of a DNA probe and a PCR based diagnostic assay for Rhizoctonia solani using a repetitive DNA sequence cloned from a Sri Lankan isolate.

Rhizoctonia solani is a destructive fungal pathogen of many economically important plants all over the world and the causative organism of sheath blight of rice in many tropical countries including Sri Lanka. A repetitive sequence from the genome of R. solani was cloned and characterized with a view to develop a DNA probe and a PCR diagnostic assay for detection of the fungus. The cloned sequence was 1550 bp long and appeared to be interspersed throughout the genome. The cloned sequence hybridized only to R. solani DNA and was sensitive enough to detect 100 pg of R. solani genomic DNA. PCR primers were designed from the cloned sequence and it was possible to develop a PCR assay for the specific detection of the fungal DNA with 10 pg sensitivity.

Genetic variation in Corynespora cassiicola: a possible relationship between host origin and virulence.

Genetic variation of 42 isolates of Corynespora cassiicola, a destructive fungal pathogen of many economically important crop plants including rubber, was investigated using RAPD-PCR analysis. Five genetic groups were identified using RAPD-PCR profiles generated by eight random primers. Results indicate that there is a significant genetic variation among C. cassiicola isolates collected from different host plants. These results should facilitate the development of rubber clones with enhanced resistance against all genetic groups of C. cassiicola.