Chemical And Biological Characterization Of A Locally Grown Ganoderma Species

Author

How Kam Chiong

Date

1999

Keyword

Ganoderma species, basidiospore, phytochemical content, antibacterial activity, antifungal activity

Abstract

Two locally grown Ganoderma species obtained from a mushroom farm in Semenyih, Malaysia were tentatively identified as G. tsugae and G. lucidum based on the morphology of basidiospores and cultural characteristics. Basidiospores of G. tsugae were 'rough' walled and had broad inter-wall pillars. Isolates of G. tsugae do not produce chlamydospores or primordia in culture and had an average growth rate of 6.8 mm/day at the optimal temperature range of 33-37°C. In contrast, the basidiospores of G lucidum appeared 'smooth' walled, characterized by narrow, numerous inter-wall pillars. Isolates of G. lucidum produce chlamydospores and primordia in culture and had a higher average growth rate of 11.8 mm/day at a lower optimal temperature range between 28-33°C as compared to G. tsugae. The fruit body of G. tsugae was investigated for its phytochemical content. Extraction followed by repeat chromatography of the hexane and methanol crude extracts resulted in the isolation of four compounds. The elucidation of structures were carried out by various spectroscopic methods. Terpenoids content were found to be present in the highest levels, followed by alkaloids, saponins and flavonoids. Chemically guided fractionations based on TLC patterns of terpenoids allowed four compounds (GM 1.1, GM 2.2, GM 3.6.5  and GM4.3) to be isolated from the hexane crude extract. These compounds were identified as stellasterol (GM 3.6.5), ergosterol (GM 4.3), di-(2-ethylhexyl) phthalate (DEHP) and a new brominated ergosta-type sterol (GM 1.1) All the fractions collected from chromatography of both hexane and methanol crude, together with the four isolated compounds were used to test for antibacterial and antifungal activity. Using 6mm-paper disc diffusion method, all fractions showed weak (7.0 to 8.9 mm) to moderate (9.0 to 10.9 mm) activity against one or more of the test microorganisms. Candida albicans was the most susceptible organism, with 35% of the fractions showing moderate activity against this opportunistic pathogen. DEHP showed a moderate broad-spectrum inhibition against the Gram-positive bacteria, Bacillus cereus and Bacillus subtilis and two fungi, Candida albicans and Schizosaccharomyces pombe. The other three ergosta-type sterols only exhibited mild activity against one or more of the test microorganism. Based on the results obtained, the occurrences of the isolated compounds were discussed.