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Studies on the extracts of black cumin (Nigella sativa L.) obtained by supercritical fluid carbon dioxide.

Suresh Kumar, T. V. (2011) Studies on the extracts of black cumin (Nigella sativa L.) obtained by supercritical fluid carbon dioxide. PhD thesis, University of Mysore.

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Abstract

The pharmacologically valued black cumin seeds of Nigella sativa L. plant of Ranunculaceae family are used in folk medicine, as they contain a complex of more than hundred phytochemicals, some of which are yet to be identified, as they are highly unstable. Of the major quinonic phenol compounds thymoquinone (TQ), dithymoquinone (DTQ), thymohydroquinone (THQ) and thymol (THY) present in the seed as bioactives, whereas thymoquinone is the most pharmacologically active compound. Conventional SoxtecTM and supercritical carbon dioxide (SCCO2) extractions were carried out for the seeds. Response surface methodology (RSM) along with Box-Behnken experimental design was employed to maximise the extract yield and TQ content by varying the temperature, pressure and material in SCCO2 extraction. The SCCO2 extraction at optimized conditions (120 bar pressure, 40°C temperature and solvent to material ratio of 45kg/kg) showed higher TQ content and lower of extract yield. SCCO2-1 extract as major volatile part (at 120 bar pressure with 40°C) and total extract obtained as SCCO2-2 (at 280 bar pressure with 50°C) and HD SCCO2 (Hydrodistillation of SCCO2-2) were chemically characterized to report 47 compounds. Of these compounds, 16 have been reported for the first time in Nigella sativa seed. The occurrence of four major quinonic phenol compounds; TQ, DTQ, THQ and THY in SCCO2-2 extract was confirmed by 2D HSQCT NMR. Further, the major bioactive compound TQ was isolated and characterized from the SCCO2-2 extract. The SCCO2 extracts showed higher antibacterial activities than SoxtecTM extracts. The isolated TQ showed lower MIC (minimum inhibitory concentration) and MBC (minimum bactericidal concentration) values against the major food borne bacteria used in this study and proved to be an antibacterial principle. Antioxidant activities were evaluated by DPPH and FRAP assays with total phenolic content (TPC), where also SCCO2 extracts indicated higher antioxidant activity than Soxtec™ extracts. The isolated TQ from SCCO2 extract proved with higher antioxidant properties and higher TPC. The synthesis of water soluble thymol glycosides was carried out using amyloglucosidase (from Rhizopus mold) and thymol with different carbohydrates in DMF (dimethyl formamide) under SCCO2 conditions. Thymol formed glycosides with D-galactose, D-mannose, Dfructose, D-ribose and D-arabinose. Spectral characterization studies revealed that the reaction occurred between the phenolic OH group of thymol and 1-O/2-O groups of D-fructose and C-1 group of D-galactose, D-mannose, D-ribose and D-arabinose resulting in monoglycosylated/arylated derivatives. Of the glycosides synthesized, thymol-6-O-D-galactopyranoside (α and β forms), thymol-6-O-D-mannopyranoside (α and β forms), thymol-6-O-2-O-D-fructofuranoside and thymol-6-O-1-O-Dfructofuranoside, thymol-6-O-D-ribofuranoside (α and β forms) and thymol-6-O-Darabinofuranoside (α and β forms) were reported for the first time. The synthesized thymol glycosides have showed better bioavailability and pharmacological properties for future applications. Hence, TQ appears to be promising as a potent natural antibacterial as well as an antioxidant principle, which could replace the synthetic antibiotics and antioxidants in food and pharmacological applications.

Item Type: Thesis (PhD)
Uncontrolled Keywords: Nigella sativa L., black cumin seeds, Phytochemicals, Supercritical carbon dioxide
Subjects: 600 Technology > 08 Food technology > 01 Analysis
600 Technology > 08 Food technology > 30 Spices/Condiments
Divisions: Food Engineering
Depositing User: Food Sci. & Technol. Information Services
Date Deposited: 16 May 2012 04:15
Last Modified: 16 May 2012 04:15
URI: http://ir.cftri.com/id/eprint/10765

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