Chemical profiling and optimization of rhoifolin extraction in relation to antioxidant properties from Fortunella polyandra

Abstract

The chemical profile and optimization of extraction process towards antioxidant response of Fortunella polyandra were studied. Essential oils from the leaves, peels, and twigs of F. polyandra were obtained by hydrodistillation and analyzed using gas chromatographymass spectrometry (GC-MS). a-Eudesmol (31.0%), hedycrayol (20.1%) and ?-eudesmol (19.7%) were the major components in the leaves oil. The most abundant components of the peels oil consisted of limonene (71.4%) and ?-terpinene (15.2%), while a-gurjunene (26.4%), hedycrayol (23.5%), and ?-eudesmol (22.1%) were the main constituents in the twigs oil. Chromatographic separation on the hexane and methanol extract has yielded lupeol and a mixture of ?-sitosterol, stigmasterol and campesterol, respectively. The chemical composition of the leaves methanolic extract was determined using ultra performance liquid chromatography coupled with quadrupole time-of-flight mass spectrometry (UPLC-QToF-MS/MS). Six flavonoid glycosides were identified and tentatively characterized as 3',5'-di-C-ß-glucopyranosylphloretin, apigenin 8-Cneohesperidoside, acacetin 6-C-neohesperidoside, acacetin 8-C-neohesperidoside, apigenin 6,8-di-C-glucoside and apigenin 7-O-neohesperidoside (rhoifolin). The influence of the extraction parameters, namely temperatures (30–70°C), times (5–15 minutes), and solvent ratios (30:70–70:30) of ethanol:water were investigated using response surface methodology (RSM) in order to determine the optimum extraction conditions that could produce maximum antioxidant activity from F. polyandra extract. Optimal extraction conditions for 2,2-diphenyl-1-picrylhydrazyl (DPPH) scavenging activity were obtained at extraction time of 5 minutes, temperature of 30°C and solvent ratio of 70:30, ethanol:water. The obtained IC50 value in the DPPH assay was 0.126±0.004 mg/mL, which is close to the predicted value of 0.137 mg/mL. The optimum parameters for ferric reducing antioxidant potential (FRAP) assay were extraction time of 5 min, temperature of 30°C, and solvent ratio of 30:70, ethanol:water. Under these conditions, rhoifolin content obtained was 67.83±0.37 ppm, which is very close to the predicted value of 67.58 ppm, whereas FRAP equivalent value of 0.22±0.01 mg/mL obtained is equal to the predicted value from the model. All three responses from the model achieved 95% confidence level. Correlation study conducted shows that there is no relationship between the rhoifolin content and the antioxidant activities of F. polyandra extract.