Abstract
The leaves of 117 plant species were extracted with methanol. After evaporation of the solvent, each aqueous residue was separated into chloroform-soluble and water-soluble fractions. The chloroform-soluble fraction was added to an artificial diet which was composed of mulberry leaf powder (50%), defatted soybean powder (24%), cellulose powder (15%), citric acid (4%), agar (5%), L-ascorbic acid (1.5%), sorbic acid (0.5%) and distilled water (2.5ml/g solid). To the diet, after evaporation of the chloroform, was added the water-soluble fraction. The diet thus prepared was fed to the 4th-instar larvae of the silkworm, Bombyx mori L., which were grown at 25°C for 6 days.
Plants tested were classified into the following five groups according to their effects on the growth of larvae. Group 1: all of the larvae died during the test period. Groups II, III and IV: strong, moderate and weak retardation of the larval growth were observed in the order of numerals. Group V: no significant effects were observed. Thirty-four species of plants were assigned to group I, and 16 to II, 19 to III, 22 to IV and 26 to V, respectively. Plants belonging to Rutaceae, Ericaceae, Taxodiaceae, Magnoliaceae and Araliaceae were found to be the most effective. The methanol extracts of 25 species showing marked efficacy were fractionated into ethyl acetate-soluble acidic, neutral and basic fractions, and ethyl acetate-insoluble aqueous fractions. The biological activities were mainly observed in the neutral fraction.
