Abstract
The sesquiterpenoids are one of major groups of antioxidants in Curcuma besides curcuminoids. However, the real substances contributing to the antioxidant activity are still unknown. In this paper, the antioxidant activity of sesquiterpenoids in four species and two essential oils from Curcuma genus was determined and compared based on TLC separation and DPPH bioautography assay. Their antioxidant capacities were quantitatively evaluated using densitometry with detection at 530 nm (λreference = 800 nm) using vitamin C as reference. The results showed that Curcuma longa rhizomes had the highest antioxidant capacity while C. phaeocaulis presented the lowest one among the four species of Curcuma. Moreover, essential oil of C. wenyujin showed higher antioxidant potential than that of C. longa. The main TLC bands with antioxidant activity of the four species of Curcuma were collected and characterized using GC-MS, and thus curzerene, furanodiene, α-turmerone, β-turmerone and β-sesquiphellandrene were determined as major sesquiterpenoids with antioxidant activity in Curcuma.
Highlights
Curcuma belongs to the family Zingiberaceae, some of which have been used as traditional Chinese medicines for a long time
The real substances contributing to the antioxidant property of essential oils from curcuma, which contain a large amount of sesquiterpenoids [4,5], are still unknown, and should be elucidated
No obvious antioxidant was found in essential oil of C. wenyujin by using online HPLC coupled with an ABTS-based assay [13]
Summary
Curcuma belongs to the family Zingiberaceae, some of which have been used as traditional Chinese medicines for a long time. Consolidating chromatographic separation and free radical scavenging activity determination allows one to evaluate the antioxidant activity of each component in the whole extract. TLC combined with DPPH bioautography assay in situ is a method has the ability to ensure the sufficient reaction and group isolation of individual components in the mixture. The active compounds were seen as clear spots against a purple background on TLC plate [14,15,16,17] It allows further isolation and characterization of the compounds by using high resolution chromatographic such as HPLC analysis [18]. Sesquiterpenoids of four species of Curcuma were separated and their antioxidant activities were determined in situ based on TLC separation and a DPPH bioautography assay. The antioxidant capacities of the four species of Curcuma were compared using vitamin C as reference
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