Evaluation of fixed oil from seeds of maesa lanceolata (myrsinaceae) for phytochemical constituents, physicochemical characteristicsand biological activity

Abstract

The present study reports the yield, physicochemical properties, phytochemical constituents and biological activities (insecticidal & antimicrobial) of M. lanceolata seed oil and compounds isolated from it. The oil was extracted by soaking the seeds in petroleum ether for five days and the isolated oil was subjected to physicochemical and phytochemical analysis employing standard test protocols available including AOAC. Pure compound isolation and characterization was carried employing chromatographic separation of crude oil, physical and spectral analysis of isolated compounds. Serial concentration range (0.3125 % to 5 %) of the crude oil and isolated compounds were evaluated for biological activities on three insect pests (S. zeamais, O. formosus and C. lectularius employing no-choice assay) & culture of five pathogenic microorganisms (B.cerus, S. aureus, E. coli, Aspargillus spp. and Fusarium spp in vitro using disc diffusion test method). Positive and negative controls were included in each test. The acid-base indicator potential of crude oil and major fraction was also evaluated using simple titration method using phenolphthalein for comparison. The seed had 30.4% oil yield. Physicochemical tests performed gave acid value (0.8±0.15), peroxide value (0.375±0.1) and saponification value (106.59±0.57). Preliminary phytochemical tests performed on the oil indicate presence of terpenoids, quinines and alkaloids. Insecticidal activities carried using the crude oil and the major fraction isolated (MLO-4) confirm both to possess concentration dependent activities on all pests tested. 100% mortality was recorded for 5.00 % test samples (MLO/MLO-4) at 9/ 6; 3½/ 3½ and 3/- hrs against Maize weevil, worker termite and bed bug respectively. The antimicrobial tests carried confirmed that crude oil and its fractions to have effect on all tested microorganisms except E. coli and Aspargillus spp. and the crude oil had better activity than its fractions. The Inhibition zones recorded (in mm) for susceptible organisms for the crude oil and its major fraction (MLO-3, (MLO-4) respectively were 9 mm, 12 mm 14 mm and (for B. cerus), crude oil and MLO-2 14 mm & 10 mm, (for S. aureus) and 11, 9, 11 and 8 (MLO, MLO-2, MLO-3 and MLO-4) respectively. The crude oil and its major fraction (MLO-4) both have shown sharp end point color change (from yellow to purple) almost similar to endpoint for Phenolphthalein. Column chromatographic separation of the crude oil led to isolation of MLO-2 (Rf 0.66). Based on spectral data ( 1 H, 13 C NMR and DEPT) and melting point data of MLO-2 we propose this compound to be an isomeric mixture of monohydrated alkylbenzoquinone.