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Abstract

The investigation of terrestrial plants origin aimed at searching new natural biologically active compounds is a central issue of this kind of studies, through structure elucidation combined with biological tests. We investigated the biologically active secondary metabolites from Leucas lavandulaefolia towards various effects on the behavior of Aphanomyces cochlioides zoospores and with antimicrobial activity. We purified the following compounds acacetin, chrysoeriol, luteolin, acacetin 7-O-β-D-glucuronide, acetoside, isoacetoside, salicylic acid and caffeic acid. Their structures were elucidated by spectroscopic analyses and compared with those of the reported data. Five compounds (luteolin, acacetin 7-O-β-D-glucuronide, acetoside, isoacetoside, and salicylic acid) were isolated from L. lavandulaefolia for the first time ever. It was found that luteolin showed a strong attractant and encystment activity toward zoospores of the phytopathogenic fungus A. cochlioides zoospores. Chrysoeriol also showed an attractant activity towards A. cochlioides zoospores. This is the first research report of L. lavandulaefolia regarding zoospores bioassay. Antibacterial assay on these compounds indicated that they have antimicrobial activity against the tested bacteria Bacillus subtilis and Staphylococcus aureus. Some of the identified secondary metabolites provided the evidence for the traditional usage of the plants as different therapeutic potentials (anti-inflammatory, antitussive and anti-diabetes) and may be useful for developing an effective control strategy to contest. INTRODUCTION: Leucas lavandulaefolia Ress. (Family-Labiatae) Syn. Leucas linifolia spreng is a well-known traditional medicinal plant widely distributed throughout South East Asia, Africa 1. It is an herbaceous annual weed, which grows abundantly in fields, pastures, roadsides and waste lands. It is erect, slightly pubescent or tomentose, 0.3 to 0.75 m in height, usually branched; branches are quadrangular, pubescent. Flowers are sub sessile or shortly pedicellate, in axillary and terminal whorls 1.3 to 2 cm diameter 1.3 to 2 cm diameter, toward the end of the branches 2 .