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Open AccessArticle

Alpha-Glucosidase and Alpha-Amylase Inhibitory Activities of Novel Abietane Diterpenes from Salvia africana-lutea

1
Chemistry Department, University of the Western Cape, Private Bag X17, Bellville 7535, South Africa
2
Oxidative Stress Research Unit, Cape Peninsula University of Technology, Symphony Rd. Bellville 7535, South Africa
3
Department of Botany, University of Fort Hare, Private Bag X1314, Alice 5700, South Africa
4
Chemistry Department, Cape Peninsula University of Technology, Symphony Rd. Bellville 7535, South Africa
*
Author to whom correspondence should be addressed.
Antioxidants 2019, 8(10), 421; https://doi.org/10.3390/antiox8100421
Received: 26 June 2019 / Revised: 16 August 2019 / Accepted: 17 August 2019 / Published: 20 September 2019
(This article belongs to the Special Issue Antioxidant Activity of Polyphenolic Plant Extracts)
The re-investigation of a methanolic extract of Salvia africana-lutea collected from the Cape Floristic Region, South Africa (SA), afforded four new abietane diterpenes, namely 19-acetoxy-12-methoxycarnosic acid (1), 3β-acetoxy-7α-methoxyrosmanol (2), 19-acetoxy-7α-methoxyrosmanol (3), 19-acetoxy-12-methoxy carnosol (4), and two known named clinopodiolides A (5), and B (6), in addition to four known triterpenes, oleanolic, and ursolic acids (7, 8), 11,12-dehydroursolic acid lactone (9) and β-amyrin (10). The chemical structural elucidation of the isolated compounds was determined on the basis of one and two dimensional nuclear magnetic resonance (1D and 2D NMR), high-resolution mass spectrometry (HRMS), ultra violet (UV), fourier transform infrared (IR), in comparison with literature data. The in vitro bio-evaluation against alpha-glucosidase showed strong inhibitory activities of 8, 10, and 7, with the half inhibitory concentration (IC50) values of 11.3 ± 1.0, 17.1 ± 1.0 and 22.9 ± 2.0 µg/mL, respectively, while 7 demonstrated the strongest in vitro alpha-amylase inhibitory activity among the tested compounds with IC50 of 12.5 ± 0.7 µg/mL. Additionally, some of the compounds showed significant antioxidant capacities. In conclusion, the methanolic extract of S. africana-lutea is a rich source of terpenoids, especially abietane diterpenes, with strong antioxidant and anti-diabetic activities that can be helpful to modulate the redox status of the body and could therefore be an excellent candidate for the prevention of the development of diabetes, a disease where oxidase stress plays an important role. View Full-Text
Keywords: diabetes mellitus; Lamiaceae; alpha-glucosidase; alpha-amylase; Salvia africana-lutea; terpenoids; cape floristic region diabetes mellitus; Lamiaceae; alpha-glucosidase; alpha-amylase; Salvia africana-lutea; terpenoids; cape floristic region
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Etsassala, N.G.; Badmus, J.A.; Waryo, T.T.; Marnewick, J.L.; Cupido, C.N.; Hussein, A.A.; Iwuoha, E.I. Alpha-Glucosidase and Alpha-Amylase Inhibitory Activities of Novel Abietane Diterpenes from Salvia africana-lutea. Antioxidants 2019, 8, 421.

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