Supercritical fluid extraction (SFE) has been developed as an alternative technique for extraction and isolation of valuable compounds from natural products without leaving toxic residues in extracts and without the risk of thermal degradation of processed products.  Cleistocalyx nervosum var. paniala (C.nervosum) is a native plant found in Northern Thailand that is commonly consumed either as fresh fruit or is used in fruit products.  Previous studies have reported that flavonoids, especially proanthocyanidin, were found in the ripe fruit of C.nervosum, and these phytochemicals are responsible for its antioxidant properties. The present study was set up to determine whether the use of SFE technique has any impacts on antioxidant abilities of C.nervosum.  One kilogram of C.nervosum ripe fruits were extracted using conventional solvent extractions (water and ethanol) and SFE using CO2 as a solvent. These extracts were then examined for total yield, total flavonoids as well as proanthocyanidin contents, and antioxidative activities.  The results showed that final yields for water, ethanol, and SFE were 0.5, 0.53, and 0.37 g/100g dry wt, respectively.  SFE contained significantly higher total flavonoids (10.65 mg/100g dry wt) and proanthocyanidin (216.08 mg/100g dry wt) contents compared to water (3.20 and 76.42 g/100g dry wt) and ethanol (6.34 and 103.25 g/100g dry wt) extract.  SFE also exhibited the greatest antioxidant properties as assessed by ABTS (0.28, 0.41, 0.60 mM trolox equivalent/g for water, ethanol and SFE, respectively), DPPH in term of % inhibition (36.45 for water, 53.08 for ethanol, and 78.41 for SFE), and FRAP (38.81 43.56, and 63.02 mM trolox equivalent/g for water, ethanol and SFE, respectively).  These findings added more profitable prospects of using SFE technique in the production of high added value products from natural plants.

Keywords: Cleistocalyx nervosum, supercritical fluid extraction, antioxidant