Browsing by Author "Grayer, R.J."

Filter results by typing the first few letters
Now showing 1 - 3 of 3
  • No Thumbnail Available
    Item
    In-vitro studies on the immunomodulatory effects of extracts of Osbeckia aspera
    (Elsevier, 2001) Nicholl, D.S.; Daniels, H.M.; Thabrew, M.I.; Grayer, R.J.; Simmonds, M.S.J.; Hughes, R.S.
    Ayruvedic medical practitioners in Sri Lanka use aqueous extracts of the mature leaves of Osbeckia aspera to treat liver disease. The extract has been shown to have hepatoprotective effects in vitro and in vivo, and to have inhibitory effects on the complement system and on in vitro phagocytosis by polymorphonuclear cells. The aim of this study was to investigate the effect of an aqueous extract of Osbeckia on lymphocyte proliferation stimulated by mitogens and antigen. In control peripheral blood mononuclear cells (PBMC), high concentrations of the Osbeckia extract were inhibitory to proliferation stimulated by phytohaemagglutinin (PHA) and tuberculin purified protein derivative (PPD). On stimulation by phorbol myristate acetate and ionomycin (PMA+I) the extract showed stimulation of proliferation at low concentrations (<10 microg/ml) with inhibition at higher concentrations. A similar inhibitory pattern on mitogen/antigen stimulation was seen with PBMC from patients with chronic hepatitis C virus (HCV) infection. These results suggest that the inhibitory agent(s) in the aqueous extract of Osbeckia may have an effect on antigen-presenting cell function. The combined hepatoprotective and immunosuppressive effects of the extract are more likely to be beneficial in acute hepatitis rather than chronic hepatitis viral infection.
  • No Thumbnail Available
    Item
    Leaf flavonoid glycosides as chemosystematic characters in Ocimum
    (Biochemical Systematics and Ecology, 1993) Grayer, R.J.; Kitea, G.C.; Veitcha, N.C.; Eckerta, M.R.; Marin, P.D.; Senanayake, S.P.; Paton, A.J.
    Abstract Thirty-one accessions of nine species belonging to three subgenera of Ocimum (basil, family Lamiaceae) were surveyed for flavonoid glycosides. Substantial infraspecific differences in flavonoid profiles of the leaves were found only in O. americanum, where var. pilosum accumulated the flavone C-glycoside, vicenin-2, which only occurred in trace amounts in var. americanum and was not detected in cv. Sacred. The major flavonoids in var. americanum and cv. Sacred, and also in all other species investigated for subgenusOcimum, were flavonol 3-O-glucosides and 3-O-rutinosides. Many species in subgenus Ocimum also produced the more unusual compound, quercetin 3-O-(6?-O-malonyl)glucoside, and small amounts of flavone O-glycosides. The level of flavonol glycosides produced was reduced significantly in glasshouse-grown plants, but levels of flavone glycosides were unaffected. A single species investigated from subgenusNautochilus, O. lamiifolium, had a different flavonoid glycoside profile, although the major compound was also a flavonol O-glycoside. This was identified as quercetin 3-O-xylosyl(1??2?)galactoside, using NMR spectroscopy. The species investigated from subgenus Gymnocimum, O. tenuiflorum (=O. sanctum), was characterised by the accumulation of flavone O-glycosides. These were isolated, and identified as the 7-O-glucuronides of luteolin and apigenin. Luteolin 5-O-glucoside was found in all nine species of Ocimumstudied, and is considered to be a key character for the genus.
  • No Thumbnail Available
    Item
    Phenolic and terpenoid constituents from the Sri Lankan medicinal plant Osbeckia aspera
    (Informa Healthcare, 2008) Grayer, R.J.; Thabrew, M.I.; Hughes, R.D.; Bretherton, S.; Lever, A.; Veitch, N.C.; Kite, G.C.; Lelli, R.
    A crude aqueous acetone extract of Osbeckia aspera. Blume (Melastomataceae), a plant from Sri Lanka used traditionally to treat liver disease, was fractionated by column and preparative paper chromatography, and the fractions were analyzed by high-performance liquid chromatography (HPLC) using diode array and mass spectrometric detection. Phenolic acids (gallic, protocatechuic, and ellagic acid), flavonol glycosides [quercetin 3-O.-β-galactopyranoside, quercetin 3-O.-β-glucopyranoside, kaempferol 3-O.-β-glucopyranoside, and kaempferol 3-O.-(6″-O.-p.-coumaroyl-β-glucopyranoside) (tiliroside)] and flavonol aglycones (quercetin and kaempferol) were identified by comparison of their retention times, UV and MS spectra with those of authentic standards. Five compounds from a methanol extract were identified by NMR spectroscopy as the flavonol glycosides, quercetin 3-O.-(3″-O.-acetyl-β-galactopyranoside) and kaempferol 3-O.-[2″,6″-di-O.-(E.,E.)-p.-coumaroyl-β-glucopyranoside], and the norsesquiterpenoids 6,9-dihydroxy-4,7-megastig-madien-3-one, 9-hydroxy-4,7-megastigmadien-3-one and 9-hydroxy-4-megastigmen-3-one. A crude water extract, 50% acetone extract and fractions from this extract, a 100% methanol extract, and three of the phenolic acids in the fractions were tested for in vitro. hepatoprotective activity against bromobenzene and 2,6-dimethyl-N.-acetyl p.-quinoneimine toxicity to HepG2 liver-derived cells. The crude water extract showed protective activity against both liver toxins, whereas the fractions and compounds were more protective against 2,6-dimethyl-N.-acetyl p.-quinoneimine than bromobenzene. Of the three phenolic acids present in the extracts that were tested, gallic and protocatechuic acids were more active at protecting the liver cells from the two toxic compounds than ellagic acid