Zahida Iqbal

Allelopathic activity of buckwheat: isolation and characterization of phenolics

Abstract Laboratory and field experiments were conducted to assess the allelopathic potential of buckwheat. In the field, buckwheat demonstrated strong inhibitory activity by suppressing weeds. In laboratory studies, aqueous and organic solvent extracts of the aerial parts of common buckwheat inhibited the root and shoot growth of lettuce seedlings. The chloroform and ethyl acetate extracts showed maximum activity, and plants grown in the presence of the ethyl acetate extract showed severe root browning. The allelopathic constituents of the ethyl acetate phase were isolated and identified as gallic acid and (+)-catechin by nuclear magnetic resonance spectroscopy. Gallic acid and (+)-catechin were present in the upper part of buckwheat at concentrations of 0.02 and 0.01%, of fresh weight, respectively. Gallic acid was found to be selectively and strongly inhibitory to root and shoot growth of tested plants at 100 and 10 μg ml−1. (+)-Catechin, however, inhibited plant growth to a lesser extent. These results suggest that buckwheat may have allelopathic potential and that when used as a ground cover crop or green manure may produce inhibitors, which could suppress weeds. Nomenclature: Buckwheat, Fagopyrum esculentum Moench; lettuce, Lactuca sativa L.

Two non-nitrogenous triterpenoids from roots of Buxus papillosa

Abstract Two new non-nitrogenous triterpenoids have been isolated from the roots of Buxus papillosa . They were characterized as 11α-hydroxy-4,4,14-trimethyl-9β,19-cyclo-5α-androst-1-ene-3,17-dione (11α-hydroxybuxatenone) and methyl 4-hydroxy-4,4,14-trimethyl-17-oxo-9(10→19) abeo -3,4-seco-5α-androsta-1(10),9(11)-dien-3-oate(buxahejrine) by extensive analysis of the spectral data.

Triterpenoid constituents of buxus papillosa

Abstract Phytochemical investigations on the leaves of Buxus papillosa have yielded a new steroidal base (-)-cyclobuxoviramine. The roots of the plant have afforded an unusual cycloartenol-type triterpenoid, (-)-buxatenone. The structures were established on the basis of 2D NMR and other spectroscopic studies.

A steroidal alkaloid from Buxus papillosa.

Abstract A new steroidal alkaloid, (−)-buxoxybenzamine, has been isolated form the leaves of Buxus papillosa and its structure elucidated.

Buxapapillosin - A New Triterpene from the Roots of Buxus papillosa

Abstract A new seco-triterpene, buxapapillosin (1) in which ring A has undergone cleavage, has been isolated from the roots of Buxus papillosa. The compound bears a cyclopropane ring found in many Buxus alkaloids and is therefore of biogenetic significance. The leaves of Buxus papillosa have also yielded three known alkaloids, buxamine A, cyclomicrobuxamine and cyclomicrobuxinine, isolated for the first time from this plant.

Isolation and identification of plant growth inhibitors from buckwheat

Fagopyrum esculentum (buckwheat), a member of the family polygonaceae, is an important forage, grain and cover crop, and has shown strong allelopathic activity in field, green house and laboratory studies. This paper describes the bioassay directed isolation and characterization of allelopathic constituents from Fagopyrum esculentum and an examination of their allelopathic potential on lettuce seedlings and some other common weeds. Methods and Materials Air-dried anal parts of Fagopyrum esculentum (2 kg) were extracted with 80 % aqueous ethanol. The extract was dried to a crude brown gum (166 g), acidified with 10% acetic acid and sequentially partitioned against hexane, chloroform, ethyl acetate and methanol (Fig. 1). The residue of the chloroform soluble fraction was found most active in the bioassay examination (Fig. 2). Therefore it was chromatographed on a column of silica gel (100 g, silica gel C-60, 70-230 mesh, Merck) and eluted with n-hexane-chloroform, and methanol. All the fractions obtained thereof were subjected to bioassay study (Fig. 3) and among these, fraction 6 was found highly inhibitory which after repeated chromatography led to the isolation of compounds 1 &2. Results and Discussion The chloroform soluble part being most inhibitory was subjected to repeated column chromatography and preparative thin layer chromatography to yield two alkaloids 1 as colorless needles (40mg) which was identified as fagomine, and 2 as yellowish white sticky substance (37 mg) which was identified as 2-piperdine methanol by NMR along with two other compounds identified as palmitic acid and abscisic acid. The 1H NMR and 13C NMR data of 1 & 2 were consistent with the published values. Compounds 1 & 2 were found strongly inhibitory and inhibited the root growth of lettuce seedlings in a dose dependent fashion. The root and shoot growth was almost diminished at 500 ppm. The 50% growth inhibition was observed at a 10 ppm (Fig. 4 & 5). Growth inhibition effects of these compounds were also determined on various weeds and were found selectively inhibitory (Fig. 6 & 7). This study demonstrates that buckwheat is selectively phytotoxic to weeds and can be used as ground cover crop. Further studies are in process to determine other constituents of buckwheat responsible for its allelopathic activity.