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  • Boswellia papyrifera Del Hochst mostly grows in Sudanian and


    Boswellia papyrifera (Del.) Hochst., mostly grows in Sudanian and Sahelian regions and their oleo-gum resin is used medically in treatment of rheumatism, menorrhagia, amenorrhoea, vaginal infections, ulcers, sores, polyuria, syphilis, bronchitis, scrofulous affections, inflammations, asthma, diarrhea, and nervous diseases [28], [29], [30]. Previous phytochemical studies on the stem bark and resins of B. papyrifera resulted in the isolation of stilbene glycosides, BAs, β-sitosterol and incensole derivatives [29], [31], [32], [33], [34], [35], [36]. The gum resins of Boswellia sacra Fluckiger (The Omani frankincense) are used against dental infections, digestive system, stomach aches, arthritis, muscle pain, as well as for the treatment of colds, fever, cough, and (+)-MK 801 [37]. However, limited reports are available on the phytochemical investigations and glucosidase activity of the title resin, BAs and frankincense obtained from these plants [37], [38], [39], [40], [41], [42]. We herein report the first α-glucosidase effect of the boswellic acids isolated from B. papyrifera and B. sacra and their synthetic derivatives along with structural-activity relationship. In addition, the molecular docking studies were also performed, in order to evaluate their mode of binding interaction with the active site of enzyme as well as in silico pharmacokinetic prediction.
    Experimental section
    Conclusion One new 3α-hydroxyurs-5:19-diene (1) together with eight known triterpenoids (2–9), two diterpenoids (10 and 11) and two straight chain alkanes (12 and 13) were isolated from the resin of B. papyrifera. Compound 2 is reported for the first time from natural source, while compounds 3–11 are reported for the first time from B. papyrifera. Compounds 1, 3, 10, 15 and 17–19 exhibited significantly better activity with an IC50 value ranging from 15.0 to 52.9 µM than the standard drug (acarbose). The molecular docking study revealed that all the active constituents well accommodate in the active site of the enzyme. Furthermore pharmacokinetic properties of the compounds were predicted in silico, suggesting that the abovementioned active compounds possesses drug like properties and excellent ADMET profile. Therefore, we can conclude that some of these α-glucosidase inhibitors obtained from resins of Boswellia species may act as leads for the future development of anti-diabetic drugs.
    Conflict of interest
    Introduction The rate of generation of glucose from the hydrolysis of glycemic carbohydrates such as starch and sucrose, in the gastrointestinal tract is highly associated with diabetes and other metabolic syndromes (Saaristo et al., 2005). Firstly, starch molecules are degraded into linear oligomers of glucose, primarily maltose and maltotriose, and branched α-limit dextrins by salivary and pancreatic α-amylases (Gray, 1975). Then, the partially digested oligomers are hydrolyzed into glucose by four α-glucosidases found in the small intestine (Dhital, Lin, Hamaker, Gidley, & Muniandy, 2013). The released monosaccharides are absorbed into the bloodstream via glucose transporters and utilized as energy throughout the body (Jones et al., 1983). Mucosal α-glucosidases comprise two complexes, maltase-glucoamylase (MGAM) and sucrase-isomaltase (SI), with similar structural and functional properties (Eskandari et al., 2011). MGAM and SI are each composed of two α-glucosidase catalytic subunits at the N and C-terminals, commonly known as maltase, glucoamylase, isomaltase, and sucrase, respectively (Lee, Quezada-Calvillo, Nichols, Rose, & Hamaker, 2012). Each α-glucosidase catalyzes specific hydrolytic effects toward different sizes of maltooligosaccharides and α-glycosidic linkages (Lee et al., 2016), but all four α-glucosidases exhibit exo-hydrolytic activity toward the non-reducing ends of α-1,4-linkages (Heymann, B. D, & Günther, 1995; Quezada-Calvillo et al., 2007). Furthermore, glucoamylase demonstrates higher hydrolytic activity toward α-1,4-linkages than the other enzymes (Lee et al., 2014), while isomaltase uniquely hydrolyzes α-1,6-linkages to break down the branched structure of starch molecules (Lin et al., 2012).