Appropriate extraction method for high contents of total phenolics, total flavonoids and free radical scavenging properties of Ziziphus mauritiana seed extracts

Abstract

Ziziphus is a genus in the family Rhamnaceae which contains about 40 species. Fruits and seeds of Ziziphus have been widely used as traditional medicines since ancient time. Z. mauritiana is a tropical or subtropical fruit tree commonly distributes in many Asian countries. The seeds of Z. mauritiana have been reported as anticancer, antidiabetic and also used to treat insomnia, reduce the body temperature and sweat. Four different extraction methods, i.e. maceration, decoction, soxhlet extraction and sonication were carried out for extracting dried powder of Z. mauritiana seeds. The solvent used for maceration, sonication and soxhlet extraction was 50% and 80% ethanol, while distilled water was used for decoction. All extracts were investigated for the yields of crude extract, free radical scavenging activity using DPPH assay, ferric reducing antioxidant power by FRAP assay, the contents of total flavonoids and total phenolics by colorimetric assay and Folin-Ciocalteau assay, respectively. Comparing between Z. mauritiana seed extracts from various extraction methods, sonication procedure provided the extracts with high total flavonoids content. However, the extract from 50% ethanol using soxhlet extraction with low temperature (60oC) exhibited good DPPH scavenging activity with EC50 of 52.91 ± 1.00 µg/mL with high total phenolics content of 27.62 ± 1.43 mg gallic acid equivalent (GAE)/g extract. The results suggested that the polyphenolic contents had high relation to antioxidant activity. Therefore, soxhlet extraction with 50% ethanol should be recommended as the appropriate extraction method for Z. mauritiana seeds for further pharmaceutical development.