Phytochemical investigation of seeds of persicaria lapathifolia and evaluation of its antimicrobial activities

Abstract

Large number of herbal remedies are used to treat microbial diseases; however, the efficacies of most of these plants have not been exhaustively investigated. Thus, the aim of this study was to isolate and characterize compounds from the seeds of Persicaria lapathifolia and evaluate their antimicrobial activities. The seeds of Persicaria lapathafolia were collected from Jimma University main campus. The air dried plant materials were ground and extracted sequentially with petroleum ether, chloroform and methanol by maceration at room temperature to give crude extract of 4 g, 34 g, and 36 g, respectively. The chloroform extract was selected for further purification following its better antibacterial activity. About 32 g of chloroform extract was subjected to column chromatography that led to the isolation of three pure compounds, named flavokawain B (1), cardamonin (2) and pashanone (3). Characterization of these compounds were done using spectroscopic techniques; mainly UV, 1D, 2D NMR, and MS. The crude extracts and isolated compounds were evaluated for their antibacterial and antifungal activity. All extracts and isolated compounds exhibited antifungal activity against Aspergillus spp and Fusarium spp. The chloroform and methanol extracts had significantly higher inhibitory effect (30 mm) against Aspergillus spp and also highest inhibition activity (15 mm) was observed for chloroform extract against E. coli. Compound 1 showed marginal activity against E. coli (9 mm), but no activity against S. aureus, Trichoderma spp and Penicillium spp. Whereas, compound 2 exhibited better zone of growth inhibition (18 mm) against S. aureus, and Trichoderma spp strains, which is comparable to that of gentamycin (19 mm) and clotrimazole (20 mm), respectively and no activity against E. coli. Compound 3 showed comparable activity against S. aureus (12 mm) and E. coli (13 mm), and also against Aspergillus spp and Fusarium spp (20 mm). Chloroform extract and compound 2 demonstrated significant antibacterial and antifungal activities with highest zone of growth inhibition against S. aureus and Trichoderma spp. which are comparable to that of reference drugs.