Antifungal Activity of Some Medicinal Plants of Sri Lanka

Thirty six medicinal plants (63 extracts) have been screened for antifungal activity against Cladosporium cladosporioides. Extracts of the following plants have displayed significant antifungal activity: Butea monosperma, Costus speclosus, Curcuma zedoaria, Eupatorium riparium, Pleiospennium alatum. Theobroma cacao i and Z~ngrber zerumbet. A preformed antifungal constituent of C. speciosus has been identified as methyl 3-(4-hydroxypheny1)-2 (E)-propenoate (1). The andfungal activity of this compound has been evaluated against Aspergillus niger, G. cladosporioides, Collerotrichum gloeosporioides, Curvularia sp. and Penicillium sp. 1.. Introduction Development of specific fungicides for use in the treatment of plant diseases is important. Plants are known t o contain antifungal compounds9, and' are a potentially useful source of these compounds. .The present study describes the investigation of 63 plant extracts derived from 36 medicinal plants of Sri Lanka. Isolation of an active constituent from the rhizome of Costus s p e c i o s u s 6 , a potential source for the diosgenin--derived steroidal drugs7 is also described. 2.1 Plant Material Plant materials used in this study, were mature (reproductive maturity) specimens collected (1-5 kg) from different localities of Sri Lanka specialIy from Central Province (Table 1). All plant varieties collected were true species. Plant specimens were identified by comparison at the National Herbarium, Royal Botanic Gardens, Peradeniya. The specimens were immediately "washed in running water tb remove contaminated soil etc. and cut into small pieces about 3-6 cm in length. The specimens were immediately airdxied and powdered in a laboratory mill. 2 B. M. R. Bandara et al. 2.2 Preparation of Plant Extracts. The air--dried plant materials (100 g) were extracted successively with (500 ml) hot hexanellight petroleum (40-60°C) dichloromethane, ethyl acetate and methanol, in a Soxhlet apparatus, or extracted directly with cold ethyl acetate and cold methanol in a bottle shaker, for a period of 48 hrs. . The solubles, were concentrated t o dryness separately using a rotavapor (below 45OC). The extracts were subjected to Cladosporium TLC-bioassay for antifungal screening as described below. 2.3 Cladosporium TLC-Bioassay Extracts (2 mg) were spotted on tlc plates (silica gel 60 PF254-366' 0.50 mm x 20 cm x 20 cm) and the plates were developed in dichloromethane. After air-drying overnight the plates were sprayed with a suspension of conidia of Cladosporium cladosporioides in Czapek-DOX nutrient solution. Plates were then incubated in a moist chamber at 25 + 2 ' ~ for 48 h.3 Inhibition areas appeared white against a background of green mycelia. The diameter of zones in which the growth was inhibited, which were approximately circular, was measured (in mm). The extracts which showed inhibition are given in the Table 1, with the Rf value and the diameter of the zone of inhibition. Benlate (0.2 mg, in methanol, 50% active ingredient, methyl-l-(butylcarbonyl)-2-benzimidazolecarbamate. Du Pont, USA) was spotted on each tlc plate as the standard fungicide.