Separation and purification of 9,10-dihydrophenanthrenes and bibenzyls fromPholidota chinensisby high-speed countercurrent chromatography

Chemodiversity of propolis samples collected in various areas of Benin and Congo: Chromatographic profiling and chemical characterization guided by 13 C NMR dereplication

INTRODUCTION

Propolis is a resinous natural substance collected by honeybees from buds and exudates of various trees and plants; it is widely accepted that the composition of propolis depends on the phytogeographic characteristics of the site of collection.

OBJECTIVES

The aim of this study was to determine the phytochemical composition of ethanolic extracts from eight propolis batches collected in different regions of Benin (north, center, and south) and Congo, Africa.

MATERIAL AND METHODS

Characterization of propolis samples was performed by using different hyphenated chromatographic methods combined with carbon-13 nuclear magnetic resonance (¹³ C NMR) dereplication with MixONat software. Their antioxidant or anti-advanced glycation end-product (anti-AGE) activity was then evaluated by using diphenylpicrylhydrazyl and bovine serum albumin assays, respectively.

RESULTS

Chromatographic analyses combined with ¹³ C NMR dereplication showed that two samples from the center of Benin exhibited, in addition to a huge amount of pentacyclic triterpenes, methoxylated stilbenoids or phenanthrenoids, responsible for the antioxidant activity of the extract for the first one. Among them, combretastatins might be cytotoxic. For the second one, the prenylated flavanones known in Macaranga-type propolis were responsible for its significant anti-AGE activity. The sample from Congo was composed of many triterpene derivatives belonging to Mangifera indica species.

CONCLUSION

Therefore, propolis from the center of Benin seems to be of particular interest, due to its antioxidant and anti-AGE properties. Nevertheless, as standardization of propolis is difficult in tropical zones due to its great chemodiversity, a systematic phytochemical analysis is required before promoting the use of propolis in food and health products in Africa.

Three new phenanthrenes from Pholidota chinensis Lindl. and their antibacterial activity

Three new phenanthrenes were isolated from Pholidota chinensis Lindl. Their structures were elucidated on the basis of spectroscopic techniques and comparison of their data to the values reported in the literature. From the 95% EtOH extract, three new compounds, namely 9, 10-dihydro-2, 4, 6-trihydroxy-7-methoxyphenanthrene (1), 11-methoxyflaccidin (2), and 2-methoxy-3,7-dihydroxy-5H phenanthro[4,5-bcd] pyran (3), were identified. Compound 3 showed an MIC₅₀ of 68.39 µM against Staphylococcus aureus subsp. Aureus.