Natural antagonists of platelet-activating factor

Occurrence, Biosynthesis, Biological activity and NMR Spectroscopy of D and B, D Ring Seco-limonoids of Meliaceae Family

Limonoids are modified tetranortriterpenoids, classified on the basis of which of the four rings (A, B, C and D) in the intact triterpene nucleus have been oxidized. The order Rutales produces a variety of seco-limonoids, such as A, B, C, D, AB, AD, and BD-ring seco-limonoids. The Meliaceae family, belonging to the order Rutales, has yielded several D-ring and B, D-ring seco-limonoids This review describes the occurrence, biosynthesis, biological activity and NMR spectroscopy of D ring seco-limonoids, such as gedunin derivatives and B, D-ring seco-limonoids, such as methyl angolensates, xyloccensins, methyl meliacates, phragmalins and modified phragmalins. The literature from 1990 to 2005 is reviewed.

Platelet-activating factor (PAF) antagonistic activity of a new biflavonoid from Garcinia nervosa var. pubescens King

The methanol extract of the leaves of Garcinia nervosa var. pubescens King, which showed strong inhibitory effects on platelet-activating factor (PAF) receptor binding, was subjected to bioassay-guided isolation to obtain a new biflavonoid, II-3,I-5, II-5,II-7,I-4',II-4'-hexahydroxy-(I-3,II-8)-flavonylflavanonol together with two known flavonoids, 6-methyl-4'-methoxyflavone and acacetin. The structures of the compounds were elucidated by spectroscopic methods. The compounds were evaluated for their ability to inhibit PAF receptor binding to rabbit platelets using ³H-PAF as a ligand. The biflavonoid and acacetin showed strong inhibition with IC₅₀ values of 28.0 and 20.4 µM, respectively. The results suggest that these compounds could be responsible for the strong PAF antagonistic activity of the plant.

Chemical composition and biological activity of the essential oil obtained from Bupleurum marginatum (Apiaceae)

Objectives

Bupleurum marginatum is a herb indigenous to the southern and southwestern part of China. It is widely used in many Chinese prescriptions. We aimed to investigate the chemical composition, antioxidant, anti-inflammatory, antimicrobial and in-vitro cytotoxic activity of the hydrodistilled and extracted essential oil from B. marginatum to validate some of its ethnopharmacologial uses.

Methods

The essential oil of the aerial parts of B. marginatum was analysed by capillary gas chromatography (GLC/FID) and gas chromatography-mass spectrometry (GLC/MS). The ability of the oil to reduce diphenylpicrylhydrazine (DPPH•) and to prevent the degradation of deoxyribose were used to evaluate the antioxidant activity. Inhibition of both prostaglandin E2 production and lipoxygenase were used to assess the anti-inflammatory activity. Antimicrobial activity was studied in vitro against a range of bacteria and fungi. The in-vitro cytotoxicity of the essential oil on six human cancer cell lines (HepG2, Caco-2, CCRF-CEM, HeLa, MiaPaCa-2 and MCF-7) was examined using the MTT assay.

Key findings

Seventy-two components, comprising almost 94.29% of the total peak area, were identified in the analysis. The main components were tridecane (13.18%), undecane (10.42%), pentadecane (8.71%), β-caryophyllene (5.53%) and β-caryophyllene oxide (5.29%). The ability of the oil to reduce diphenylpicrylhydrazine (DPPH•) and to prevent the degradation of deoxyribose were used to evaluate the antioxidant activity and the corresponding IC50 values (drug concentration which resulted in a 50% reduction in inhibition of the activity) were found to be 3.66 mg/ml and 17.4 μg/ml, respectively. Inhibition of both prostaglandin E2 production and lipoxygenase were used to assess the anti-inflammatory activity (IC50 of 63.64 μg/ml for lipoxygenase, 26.04% inhibition of prostaglandin E2 at 25 μg/ml dose). The oil also showed a significant in-vitro antimicrobial activity against Gram positive pathogens (Streptococcus pyogenes and Streptococcus agalactiae) with minimum inhibitory concentration (MIC) values ranging from 0.125 up to 4.00 mg/ml. The in-vitro cytotoxicity of the essential oil on six human cancer cell lines (HepG2, Caco-2, CCRF-CEM, HeLa, MiaPaCa-2 and MCF-7) examined using the MTT assay revealed the highest activity to be in the CCRF-CEM cell line with an IC50 (concentration which resulted in a 50% reduction in cell viability) of 46.01 μg/ml after 24 h treatment.

Conclusions

The essential oil of B. marginatum exhibited a promising anti-inflammatory activity along with strong cytotoxicity against many cancer cells (CCRF-CEM and HepG2) mediated through induction of apoptosis, and this in-vitro activity make its local traditional uses rational. However, its limited antimicrobial activity indicates that a combination with other drugs is essential for effective use. Further selectivity testing is required to evaluate the effect of the oil against normal cells.

A concise synthesis of ginkgolide M, a minor component of a terpene trilactone fraction from ginkgo biloba roots

Ginkgolide M (GM), which is found only in the roots of the Ginkgo biloba tree and is an inhibitor of ligand-operated ion channels in the central nervous system, has been prepared in three steps from 10-benzylginkgolide C, an intermediate generated during the isolation and separation of ginkgolides from Ginkgo biloba leaf extract. The described synthetic sequence can be applied to access GM derivatives for biological studies.

The role of platelet activating factor in allergic inflammation

It is becoming increasingly apparent that platelet activating factor (PAF) is an important mediator in allergic disease. It is synthesized by a variety of cells including those which are thought to participate in the inflammatory process. In turn, PAF may stimulate these cells which further propagates the inflammatory process. Furthermore, PAF can mimic most of the characteristics which are relevant in allergic inflammation and PAF can produce effects comparable to that produced by antigen in animal models of allergic inflammation and in man. Other evidence to support the involvement of PAF in allergic disease has also arisen with the advent of PAF antagonists. Many PAF-induced responses can be attenuated by these agents and many antigen-induced responses in both animal models and in man can also be attenuated by PAF antagonists. This review attempts to summarize the results from studies which have investigated the role of PAF in allergic inflammation and the effects of PAF antagonists against both PAF and allergic-induced responses.