Antioxidant activity of essential oil of three cultivars of Amomum subulatum and standardization of high performance thin layer chromatography (HPTLC) method for the estimation of 1,8-cineole

Essential oils of the fruits of three cultivars of Amomum subulatum (Family-Zingiberaceae), such as varlangy, seremna and sawney were isolated. Antioxidant potential was determined using 1,1-diphenyl-2-picrylhydrazyl (DPPH) and 2,2'-azino-bis(3-ethylbenzothiazoline-6-sulphonic acid) (ABTS) scavenging and FeCl3-reducing models and the presence of 1,8-Cineole was quantified using the developed high performance thin layer chromatography (HPTLC) method. In the DPPH scavenging model, the IC50 value of the essential oil of the seremna, varlangy and sawney were found to be 172.3, 216.9 and 274.3 μg/ml, respectively, while in the ABTS scavenging model, the IC50 value of the seremna, varlangy and sawney were found to be 27.96, 31.34 and 32.49 μg/ml respectively. The antioxidant power of the FeCl3 reducing model, the absorbance value of the essential oil of the seremna was found comparatively higher than the essential oils of varlangy and sawney. The content of 1,8-cineole was determined by the developed HPTLC densitometric method, and the value of the percentage (mean ± SD, % w/w) content of the essential oils  of the seremna, varlangy and sawney were found to be 69.59 ± 1.45%, 48.78 ± 3.21 and  47.84 ± 1.76 respectively. The highest antioxidant value of seremna cultivar may be due to the presence of high content of 1, 8-cineole. The HPTLC method, therefore confirms that monoterpene 1,8-cineole is the main antioxidant compound present in the fruits of A. subulatum.   Key words: Amomum subulatum, cultivars, essential oil, 1,8-cineole, high performance thin layer chromatography (HPTLC), antioxidants.