Thesis (M.Sc.)--Chulalongkorn University, 2009

A new naphthalene derivative, AS21B-4 (4), was obtained from the EtOAc extract of an endophytic fungus, Rhytidhysteron sp. isolated from Azima sarmentosa Benth. & Hook., which was cultured on Malt extract broth, along with four konwn compounds, MK3018 (1), palmarumycin CR1 (2), 4-O-methyl-CJ12372 (3) และ 4-O-methyl- CJ12371 (5). Additionally, four new sesquiterpenes, merulins A-D (6-9), were isolated from the extract of another fungus (Basidiomycetous) of Xylocarpus granatum Koenig. cultured on Corn steep broth medium. The structures of these compounds were elucidated on the basis of spectroscopic studies. Further, all isolated compounds were evaluated for their antimalarial, cytotoxic and antibacterial activity. Compounds (8) and (9) exhibited potent antimalarial activity with IC₅₀ values of 0.39 and 1.35 µM, respectively, while compounds 1 and 3-6 were moderately active. For compound 2, it showed to be inactive in this assay. Additionally, all naphthalene derivatives (1-5) exhibited nonselective toxicity toward all cell lines tested. Merulins A (6), C (8) and D (9) also showed moderate activity against all cell lines, except for CHAGO cell lines, whereas merulin B (7) exhibited moderate cytotoxicity selectively against only Hep-G2 cell lines. Moreover, all compounds (1-9) were active toward different bacterial strains with different MIC values