Effects of Extraction Solvents and Drying Techniques on Antioxidant Content and Radical Scavenging Activity of Roselle (Hibiscus sabdariffa) Calyx
Effects of Extraction Solvents and Drying Techniques on Antioxidant Content and Radical Scavenging Activity of Roselle (Hibiscus sabdariffa) Calyx
Nur Anis Hashim1, Nor Hasima Mahmod1*, Abubakar Abdullahi Lema2, Lee-Hoon Ho3 and Mohammad Moneruzzaman Khandaker1
ABSTRACT
Abstract | Hibiscus sabdariffa or roselle is well known for its high antioxidant content. This species is originated in West Africa and spread to Asia by the colonials in 1700s. The optimal conditions for the preparation of dried materials for further processing and suitable drying techniques while preserving their antioxidants have yet to be inferred. Thus, the present study aims to determine the content and activity of the antioxidants in fresh and dried roselle calyx. The random sampling technique was applied by collecting the calyx roselle from different plants. Calyx samples were labeled as fresh calyx (FC), air-dried (AD), oven-dried (OD), and freeze-dried (FD) according to treatments. Four extracting solvents, which were methanol, ethanol, aqueous, and hexane, were evaluated for their efficiency in extracting antioxidant components from the differently treated roselle calyx, and these extracts were used to determine antioxidant activities and contents by assessing DPPH scavenging activity, total phenolic content (TPC) and total flavonoid content (TFC). Next, the samples were subjected to qualitative phytochemical screenings. DPPH scavenging activity was the highest in an FC sample extracted by methanol with 81.697 mg/mL. The highest TPC was measured in an OD sample extracted by ethanol (172.04 ±0.43) and the most TFC was found in FC ethanol extract (22.9±0.03). Among the fresh calyx and three drying methods investigated, FC in ethanol produces the highest potential in antioxidant activity, followed by FD, AD and OD. Phytochemical screening tests found that the fresh and freeze-dried calyx possessed important antioxidative metabolites such as anthocyanins, tannins, saponins, glycosides, flavonoids and terpenoids. The findings demonstrated that fresh calyx retained the highest antioxidant capacity, thus providing insights into post-harvest processing of the calyx.
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August 2024
Vol. 40, Sp. Iss. 1
