Abstract
<p>The effect of average particle sizes (APS: 0.45 and 1.01 mm), solvent types (ST: distilled water, 2% citric acid solution, and 50% ethanol), and extraction times (ET: 40, 50, and 60 min) on the physicochemical properties, antioxidant capacity, and half maximal effective concentration (EC50) in calyces of Roselle (Hibiscus sabdariffa) was analyzed. The extracts obtained with distilled water and 2% citric acid solution had an intense red color which purities (C) were 78.5 ± 2.3 and 79.8 ± 2.2, respectively. The alcoholic extracts showed a dark red color (C = 75.9 ± 1.8). The alcoholic (820.2 ± 73.7 mg Trolox equivalents (TE)/100 g dry calyces) and acid extracts (773.34 ± 53.0 mg TE/100 g dry calyces) showed higher antioxidant capacity than the aqueous extracts (673.24 ± 116.0 mg TE/100 g dry calyces). The EC50 value was better for the alcoholic extracts, followed by the 2% citric acid extracts and finally by the aqueous extracts (13.4 ± 1.0, 14.9 ± 1.0, and 17.2 ± 1.2 mg of extract, respectively). According to results, the best antioxidant properties were achieved using an APS of 0.45 mm, 50:50% ethanol:water ratio, and ETs of 30 or 45 min.</p>
Highlights
In recent years, it has been a great interest for researching about the antioxidant properties of many vegetable products consumed by humans
The absorbance was measured at 517 nm using a Cary 100 UV-visible spectrophotometer (Varian Inc., Palo Alto, CA, USA)
The greater weights of fine powder were retained in the sieves of 0.3 mm (24.42 ± 1.98%) and 0.6 mm (28.99 ± 4.11%); the greater weights for the ground powders were retained in the sieves of 1.0 (21.66 ± 03.3%), 1.4 mm (31.76 ± 1.26%), and 2.0 mm (18.80 ± 1.68%)
Summary
It has been a great interest for researching about the antioxidant properties of many vegetable products consumed by humans. Several researchers have pointed out that Roselle extracts may have various therapeutic effects; one of them is the antioxidant capacity, attributed mainly to the content of anthocyanins and phenolic compounds (Tsai, Mcintoshb, Pearceb, Camdenb, & Jordanc, 2002; Tsai & Huang, 2004; Anokwuru, Esiaba, Ajibaye, & Adesuyi, 2011; Amer, El-Sharkawy, Abdel Bar, & Ashour, 2012). It has been reported higher antioxidant capacity in Roselle calyces of red variety than in the white one variety (Christian & Jackson, 2009)
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