The effect of extraction process on polyphenol content, triterpene composition and bioactivity of yellow birch (Betula alleghaniensis Britton) extracts

Crude ethanol extracts from different tissues of Betula alleghaniensis: wood, inner and outer bark, foliage, and twigs were evaluated for their nitric oxide (NO)-radical scavenging activities and inhibitory effects on the production of NO in LPS/INF gamma-stimulated RAW 264.7 macrophages. As a renewed interest in plant-derived drugs has led to an increased need for efficient extraction methods, ultrasonic-assisted extraction (UAE) was investigated and compared with conventional maceration. The lower energy consumption by the UAE process compared to maceration determined in our study qualifies also this extraction as an environmentally friendly process. Our results indicate that the foliage extract has the most potent radical scavenging capacity while wood and twigs extracts exert the highest inhibitory effects on the production of NO in LPS/INF gamma-stimulated RAW 264.7 macrophages. Extracts obtained by UAE present lower cytotoxic activity on RAW cells. Our results also demonstrate that ultrasounds help to selectively extract the bioactive molecules from foliage, twigs and wood, which inhibit the production of NO by macrophages. The highest total phenol content has been determined for the inner bark extracts and the flavonoids are the major phenolics present in foliage extracts. Poor correlations determined between the total phenols and radical scavenging capacity of the extracts indicates to the synergistic or antagonist effects of molecules present, various polyphenols and triterpenes being identified in the extracts studied in this research. (C) 2009 Elsevier B.V. All rights reserved.