Antioxidant and Phytochemical Potential of and Phytochemicals in Gymnema inodorum (Lour.) Decne in Northern Thailand

Gymnema inodorum (Lour.) Decne is a vegetable local to Chiang Mai Province of Northern Thailand. This study aimed to analyze the antioxidant and phytochemical potential of G. inodorum found in Chiang Mai Province; antioxidant compounds of G. inodorum were tested via DPPH, ABTS and FRAP assays, and total phenolic compound and total flavonoid contents were analyzed. Anti-inflammatory effects were focused on regarding pharmacological potential. The gymnemic acid level was analyzed by HPLC-UV, and other potential chemicals were analyzed by LC-QTOF/MS. The quantifications of gymnemic acid contents analyzed using HPLC-UV showed that the highest gymnemic acid concentrations were found in the air-dried and roasted 1-day-fermented leaf extracts (0.1258 ± 0.0157 μg/mg). The highest free radical scavenging activity via DPPH assay was found in baked leaf extract, with an IC(50) of 8.99 mg/mL, and via ABTS assay in baked and roasted leaf extracts, with an IC(50) of 1.05 mg/mL. FRAP assays showed the highest free radical scavenging activity for the baked leaf extract, with 0.0085 ± 0.008 mM Fe(2+)/g sample. The total phenolic contents of fresh G. inodorum leaf extracts obtained with ethanol, methanol and water were 0.19 ± 0.0004, 0.21 ± 0.0010 and 0.10 ± 0.0008 μg GAE/g, respectively. The total flavonoid contents of fresh G. inodorum leaf extracts obtained with ethanol, methanol and water were 74.56 ± 28.00, 71.88 ± 16.11 and 10.74 ± 3.63 μg QE/g, respectively. The LC-QTOF/MS analysis of the fresh G. inodorum leaf extract showed that 6-hydroxykaempferol 7-rutinoside was the most abundant compound. In the study, G. inodorum, a plant local to Northern Thailand, is shown to be a useful plant with high antioxidant and phytochemical potential properties.