Isolation and characterization of apigenin 6,8-di-c-glycocides derivatives from ficus deltoidea var. trengganuensis / Hidayatul Atiqah Abd Karim

Ficus deltoidea belongs to the family of Moraceae and locally known as “mas cotek”. Mas cotek is traditionally used to treat diabetes and many products have been sold in the market especially as herbal tea products. To date, only four compounds were isolated and characterized from Ficus deltoidea even though there were many scientific reports on its biological activities. A list of identified compounds published using mass spectrometry (MS) cannot determine the exact structure of pentose sugars and its stereochemistry. Most of the reports did not state variety of Ficus deltoidea used. Correct identification of compounds especially to Ficus deltoidea specific varieties is crucial for reproducibility and consistency of its biological activity and as quality control for mas cotek-based products. Therefore, this study is conducted to isolate and characterize chemical constituents in one of Ficus deltoidea variety namely trengganuensis. The dried leaves were soaked in methanol and the profile of the crude extract was developed using ultra high performance liquid chromatography (UHPLC) before introduced to resin column to remove free sugar and fractionated using preparative liquid chromatography (PLC). Purification of fractions containing apigenin 6,8-di-C-glycosides derivatives was a challenging task as they had very close retention times. The isolation was successfully accomplished using repeated preparative recycling high performance liquid chromatography (PRHPLC) in isocratic condition. The structures of these pure compounds were elucidated by using ultraviolet (UV), nuclear magnetic resonance (NMR) and MS. This exhaustive chromatographic procedures led to the isolation of nine apigenin 6,8-di-C-glycosides derivatives, namely vicenin-2 (65), vicenin-1 (66), schaftoside (53), isoschaftoside (54), apigenin 6-C-β-L-arabinopyranosyl-8-C-α-L-arabinopyranoside (67), apigenin 6,8-di-C-α-L-arabinopyranoside (68), apigenin 6-C-β-D-xylopyranosyl-8-C-α-L-arabinopyranoside (69), apigenin 6,8-di-C-β-D-xylopyranoside (70) and apigenin 6-C-α-L-arabinopyranosyl-8-C-β-D-xylopyranoside (71). All compounds are apigenin as aglycone and have two sugar moieties at C-6 and C-8 of apigenin. The sugar can be glucose, xylose or arabinose. The configuration of glucose and xylose often exist as D sugar while arabinose as L sugar. They have interconverting of α and β positions at C-6 and C-8. Some of them are isomers. All compounds are C-glycosides as their anomeric carbon fall in the range between 70 to 80 ppm. This is the first phytochemical study that reported specifically to variety specific of Ficus deltoidea namely Ficus deltoidea var. trengganuensis. The isolated compounds were reported for the first time in the family of Moraceae except 53 and 54, which were previously isolated from Ficus carica. These isolated compounds were unique as they only present in genus Ficus.