Abstract
We analysed four different Sudanese roselle samples for their potential as novel xanthine oxidase (XO) inhibitors. Phytochemical screening showed the presence of polyphenols, flavonoids, organic acids, saponins and sterols in all samples. Liquid chromatography with tandem mass spectrometry (LC-MS/ MS) was used to identify and characterise five anthocyanins in all samples: cyanidin-3-glucoside (cy-3-glu), delphinidin-3-sambubioside (dp-3-sam), cyanidin-3-rhamnoside (cy-3-rhm), delphinidin-3‑rhamnoside (dp-3-rhm) and pelargonidin-3-glucoside (pg-3-glu). Identification of cy-3-rhm, dp-3-rhm and pg-3-glu confirmed the selectivity and sensitivity of LC-MS as a powerful technique for identifying anthocyanins. In silico studies of the identified anthocyanins were performed to explore their promising inhibitory activity toward XO. Interactions between the ligand and the enzyme were via the H-bond, and hydrophobic (π-alkyl, π-sigma and alkyl) and/or electrostatic (π-cation) bonds. Inhibition of the anthocyanins was compared with that of topiroxostat, a commercial drug for hyperuricaemia. Dp-3-rhm was the most active inhibitor with a binding energy of ca. -10.90 kcal/mol compared to topiroxostat’s binding energy of ca. -8.60 kcal/mol. The good inhibition results obtained from anthocyanins toward XO suggest their application as a drug candidate to treat gout and other diseases related to the activity of XO.Significance: Sudanese roselle is rich in phytochemicals, particularly polyphenols and anthocyanins. The isolated anthocyanins in this study were explored as novel potential XO inhibitors. Further pharmacological and clinical studies are necessary for the development of new potential anthocyanin drugs to treat gout and other diseases related to XO increased activity such as hypertension.
Highlights
Sudanese roselle is rich in phytochemicals, polyphenols and anthocyanins
Further pharmacological and clinical studies are necessary for the development of new potential anthocyanin drugs to treat gout and other diseases related to xanthine oxidase (XO) increased activity such as hypertension
Our results show that roselle is rich in phytochemicals, especially anthocyanins, in agreement with the results of previous studies.[3,4,5]
Summary
Hibiscus sabdariffa L. – commonly known as roselle, hibiscus and karkade – is an annual or perennial plant that grows in tropical and subtropical regions of the world including Sudan.[1,2,3] Its calyces are characterised by a sour taste, brilliant red colour, and pleasant aroma that gives the plant its commercial importance.[3,4]Roselle, like other plants, possesses phytochemical compounds such as tannins, saponins, glycosides, phytosterols, minerals, organic acids, and antioxidants like polyphenols, flavonoids, and vitamins.[2,4,5] These compounds occur naturally in different parts of the plants and they are characterised by their protective and preventive properties against several diseases.[6]The calyces of roselle are rich in anthocyanin pigments; anthocyanins are water-soluble plant pigments responsible for providing the colours to almost all plant tissues.[7,8,9] In various plant tissues, anthocyanins vary in amount and type according to composition and chemical structures.[7]. Sudanese roselle is rich in phytochemicals, polyphenols and anthocyanins. Our results show that roselle is rich in phytochemicals, especially anthocyanins, in agreement with the results of previous studies.[3,4,5] The general screening of some phytochemical constituents detected the presence of polyphenols, flavonoids, saponins, and sterols, and an absence of anthraquinones.
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