Antimicrobial and antioxidant activity of kaempferol rhamnoside derivatives from Bryophyllum pinnatum.

BACKGROUND: Bryophyllum pinnatum (Lank.) Oken (Crassulaceae) is a perennial succulent herb widely used in traditional medicine to treat many ailments. Its wide range of uses in folk medicine justifies its being called "life plant" or "resurrection plant", prompting researchers' interest. We describe here the isolation and structure elucidation of antimicrobial and/or antioxidant components from the EtOAc extract of B. pinnatum. RESULTS: The methanol extract displayed both antimicrobial activities with minimum inhibitory concentration (MIC) values ranging from 32 to 512 µg/ml and antioxidant property with an IC50 value of 52.48 µg/ml. Its partition enhanced the antimicrobial activity in EtOAc extract (MIC = 16-128 µg/ml) and reduced it in hexane extract (MIC = 256-1024 µg/ml). In addition, this process reduced the antioxidant activity in EtOAc and hexane extracts with IC50 values of 78.11 and 90.04 µg/ml respectively. Fractionation of EtOAc extract gave seven kaempferol rhamnosides, including; kaempferitrin (1), kaempferol 3-O-α-L-(2-acetyl)rhamnopyranoside-7-O-α-L-rhamnopyranoside (2), kaempferol 3-O-α-L-(3-acetyl)rhamnopyranoside-7-O-α-L-rhamnopyranoside (3), kaempferol 3-O-α-L-(4-acetyl)rhamnopyranoside-7-O-α-L-rhamnopyranoside (4), kaempferol 3-O-α-D- glucopyranoside-7-O-α-L-rhamnopyranoside (5), afzelin (6) and α-rhamnoisorobin (7). All these compounds, except 6 were isolated from this plant for the first time. Compound 7 was the most active, with MIC values ranging from 1 to 2 µg/ml and its antioxidant activity (IC50 = 0.71 µg/ml) was higher than that of the reference drug (IC50 = 0.96 µg/ml). CONCLUSION: These findings demonstrate that Bryophyllum pinnatum and some of its isolated compounds have interesting antimicrobial and antioxidant properties, and therefore confirming the traditional use of B. pinnatum in the treatment of infectious and free radical damages.

Chemical constituents of Millettia barteri and their antimicrobial and antioxidant activities.

CONTEXT: Millettia barteri (Benth.) Dunn (Fabaceae) is an African medicinal plant used in folk medicine to treat many diseases. This species, as well as other Mellettia species, has been of interest to researchers because of their wide range of traditional uses. OBJECTIVE: Phytochemical, antimicrobial and 2,2-diphenyl-1-picryl-hydrazyl-hydrate (DPPH)-radical scavenging investigations of the hexane and EtOAc extracts of the stem bark of M. barteri were carried out here for the first time. MATERIALS AND METHODS: The isolation of compounds was done through silica gel column chromatography and their structures were established using spectroscopic analysis, especially, 1D NMR in conjunction with 2D experiments (COSY, HMQC and HMBC), and physical data compared with literature values. The broth micro dilution method was used for antimicrobial test while DPPH radical scavenging assay was used for antioxidant test. RESULTS: Seven compounds, including two guanidine alkaloids: millaurine (2) and milletonine (7); one flavonoid: afzelin (6); four sterols: ß-sitosterol (1), ß-sitosterol glucoside (3), mixture of stigmasterol (4) and ß-sitosterol (5) palmitates have been isolated from stem bark of hexane and ethyl acetate extracts of M. barteri. These extracts showed antimicrobial activity on the set of germs tested with minimum inhibitory concentration values varying from 64 to 512 µg/mL, as well as antioxidant activity (IC50 62.74 and 77.23 µg/mL). Compounds 2 and 7, tested for the first time, demonstrated antimicrobial and antioxidant activities. DISCUSSION AND CONCLUSIONS: The present study clearly demonstrated that M. barteri and some of its isolates possess antimicrobial and antioxidant properties and may act as potential antioxidant for biological systems susceptible to free radical-mediated reactions.