Isolation and Structural Confirmation of Xanthone Isomers from Dryopteris ramosa (Hope) C. Chr. and Their In Vitro Antio
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RESEARCH ARTICLE-BIOLOGICAL SCIENCES
Isolation and Structural Confirmation of Xanthone Isomers from Dryopteris ramosa (Hope) C. Chr. and Their In Vitro Antioxidant Mechanism Muhammad Ishaque1 · Yamin Bibi1 · Abdul Qayyum2
· Marcello Iriti3
Received: 10 May 2020 / Accepted: 31 October 2020 © King Fahd University of Petroleum & Minerals 2020
Abstract The long history of using plant species as medicines worldwide provides clues for the search for bioactive phytochemicals. One of the important traditional medicinal plant species of Pakistan is Dryopteris ramosa (Dryopteridaceae). The fronds of Dryopteris ramosa are traditionally used for the treatment of gastric ulcer and constipation. The crude methanol extract and aqueous fraction of Dryopteris ramosa exhibited strong free radical scavenging potential. Two xanthonoid compounds, mangiferin and isomangiferin, were isolated from the aqueous fraction of Dryopteris ramosa by chromatographic techniques (CC Sephadex LH20, followed by MPLC and purified by preparative TLC). Their structures were confirmed by spectroscopic analysis MS, NMR (1H, 13C, HSQC and HMBC). This is the first report on isolation of mangiferin and isomangiferin from Dryopteris genus though previously reported in other fern genera, e.g., Cystopteris, Acystopteris, Gymnocarpium and Asplenium. The antioxidant potential of mangiferin (60.34 ± 0.14 μg/mL) and isomangiferin (55.98 ± 0.39 μg/mL) was comparable to ascorbic acid (57.97 ± 0.93 μg/mL), thus representing promising antioxidant agents against oxidative stress. The investigation of the mechanism of free radical scavenging by mangiferin and isomangiferin showed that the catechol moiety was involved in quenching of free radicals. This study justified the traditional use of Dryopteris ramosa confirming the pharmacological properties of isolated compounds. Further phytochemical studies on Dryopteris ramosa are needed for identification of new bioactive phytochemicals in this plant of ethnobotanical relevance. Keywords Pteridophytes · Dryopteridaceae · Mangiferin · Isomangiferin · Dryopteris ramosa
1 Introduction The traditional medicine and ethnomedicinal knowledge have emphasized the healthy potential of herbal remedies. The natural products have evolved in biological systems where they exert a variety of functions including scavenging of free radicals, protecting the cells from oxidative stress and pathogens, and the living organisms from detrimental environmental factors. Noteworthy, during the period 1981 to 2010, a total of 1073 organic molecules have been intro-
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Abdul Qayyum [email protected]
1
Department of Botany, Pir Mehr Ali Shah-Arid Agriculture University Rawalpindi, Rawalpindi 46300, Pakistan
2
Department of Agronomy, The University of Haripur, Haripur 22620, Pakistan
3
Department of Agricultural and Environmental Sciences, Milan State University, Via G. Celoria 2, 20133 Milan, Italy
duced as medicines worldwide out of which more than 50% were plant natural products [1]. Ferns are popular as food, fibers, crafts, building mate
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