Phytochemical investigation of the stem bark extract of Boswellia papyrifera afforded two new stilbene glycosides, trans-4',5-dihydroxy-3-methoxystilbene-5-O-{alpha-L-rhamnopyranosyl-(1-->2)-[alpha-L-rhamnopyranosyl-(1-->6)]-beta-D-glucopyranoside (1), trans-4',5-dihydroxy-3-methoxystilbene-5-O-[alpha-L-rhamnopyranosyl-(1-->6)]-beta-D-glucopyranoside (2), and a new triterpene, 3alpha-acetoxy-27-hydroxylup-20(29)-en-24-oic acid (3), along with five known compounds, 11-keto-beta-boswellic acid (4), beta-elemonic acid (7), 3alpha-acetoxy-11-keto-beta-boswellic acid (8), beta-boswellic acid (9), and beta-sitosterol (10). The stilbene glycosides exhibited significant inhibition of phosphodiesterase I and xanthine oxidase. The triterpenes (3-9) exhibited prolyl endopeptidase inhibitory activities.

Antioxidant activity test using two different methods namely 2,2-diphenyl-1-picrylhydrazyl and 2,2'-azinobis(3-ethylbenzothialozinesulfonate) diammonium salt free radical scavenging test has been carried out on three Cameroonian plant extracts used in the treatment of intestinal and infectious diseases: Pittosporum mannii Hook f. (Pittosporaceae), Vepris heterophylla R. Letouzey (Rutaceae) and Ricinodendron heudelotii (Baill) Pierre ex Pax (Euphorbiaceae). Results of this study in the 2,2-diphenyl-1-picrylhydrazyl scavenging test show that the ethyl acetate extract of P. mannii and the methanol extract of V. heterophylla exhibit high free radical scavenging activities with IC50 values of 177.74 and 204.69 μg/ml, respectively while the methanol/dichloromethane (1+1) extract of R. heudelotii showed weak free radical scavenging activities as compared to Trolox (939.19 μg/ml) used as standard. In the same manner, 2,2'-azinobis(3-ethylbenzothialozinesulfonate) diammonium salt radical scavenging test of these extracts was in accordance of the result of 2,2-diphenyl-1-picrylhydrazyl test. The antioxidant properties of these extracts probably explain partly, the use of these plants in traditional medicine for the treatment of infectious diseases and inflammations.