The anticomplementary activity of compounds isolated from the heartwood of Caesalpinia sappan L. (Leguminosae) was investigated. The sterol mixture (campesterol 11.2%, stigmasterol 18.9% and beta-sitosterol 69.9%) was most potent and brazilin, brazilein, and protosappanin E showed a new anticomplementary activity on the complement system in vitro.

As part of the search for anticomplementary active components from natural products, the anticomplementary properties of methanolic extracts from the flower buds of Magnoliafargesii have been investigated. Bioassay-guided chromatographic separation of the active constituents led to the isolation of compound 1, whose structure was identified by spectroscopic methods to be kaempferol 3-O-beta-D-(6"-O-coumaroyl)glucopyranoside (tiliroside). Tiliroside showed very potent anti-complement activity (IC50=5.4 x 10(-5) M) on the classical pathway of the complement system, even higher than rosmarinic acid, which is a well-known inhibitor against the complement system. On the other hand, the hydrolysates of tiliroside, kaempferol, astragalin and p-coumaric acid showed very weak activity on this system.

In a search for platelet-activating-factor (PAF) antagonists, two new lignan compounds were isolated from the Chinese crude drug shin-i, the flower buds of Magnolia fargesii. Their structures were elucidated as (2S,3R,4R)-tetrahydro-2-(3,4-dimethoxyphenyl)-4-(3, 4-dimethoxybenzoyl)-3-(hydroxymethyl)furan (magnone A, 1) and (2S,3R, 4R)-tetrahydro-2-(3,4,5-trimethoxyphenyl)-4-(3, 4-dimethoxybenzoyl)-3-(hydroxymethyl)furan (magnone B, 2). Magnones A and B showed antagonistic activity against PAF in the [3H]PAF receptor binding assay with the IC50 values of 3.8 x 10(-5) M and 2.7 x 10(-5) M, respectively.

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The roots of Dipsacus asper have yielded two new triterpenoid saponins, dipsacus saponins B [1] and C [2], which have been characterized by chemical and spectral means and spectral means as hederagenin-3-O-beta-D-glucopyranosyl-(1-->4)-[alpha-L-rhamnopy ran osyl- (1-->6)]-beta-D-glucopyranosyl-(1-->3)-alpha-L-rhamnopyranosyl-(1-->2)-a lpha- L-arabinopyranoside [1] and hederagenin-3-O-beta-D-xylopyranosyl-(1-->4)- beta-D-glucopyranosyl-(1-->4)-beta-D-glucopyranosyl-(1-->3)-[alpha-L- rhamnopyranosyl-(1-->4)]-alpha-L-rhamnopyranosyl-(1-->2)-alpha-L- arabinopyranoside [2].

A very high content (at least 0.23%) of ergosterol peroxide was isolated fromNaematoloma fasciculare Karst. Not only ergosterol peroxide but also ergosterol showed very strong anticomplementary activity on the classical pathway, the IC(50) values being 5.0 muM and 1.0 muM, respectively. The(1)H and(13)C NMR data of ergosterol peroxide were revised and completely assigned by DEPT,(1)H-(1)H COSY, HMQC and HMBC correlations.

Ginseng saponins and their degradation products have been screened for antagonist activity towards [3H]PAF (platelet activating factor) in washed rabbit platelet receptor binding studies. 20(S)- and delta20-ginsenosides Rg3, protopanaxadiol-type saponins, were found to be relatively potent PAF antagonists (IC50 = 4.9 x 10(-5) M and 9.2 x 10(-5) M, respectively).