Variations in metabolomic profiles of populations of the medicinal plant Sutherlandia frutescens in South Africa

Sutherlandia frutescens (L.) R.Br., Family Fabaceae, is a multi-purpose traditional phytomedicine endemic to southern Africa [1]. It is used to treat various ailments such as diabetes, stress, wounds and is notably used to treat cancers [2]. S. frutescens has a wide distribution in South Africa and there is limited information with regards to its phytochemical variation between samples growing in distinct geographical areas. The aim of this study was to elucidate the chemical variations among selected populations of S. frutescens using a metabolomic profiling through an LC-MS technique. Sutherlandiosides, a set of unique triterpene glycosides used as biomarkers in commercial Sutherlandia material, were used as a basis for measurement of chemical variation. Liquid chromatography mass spectrometry in tandem with chemometric analysis were used to assess the metabolite contents and variation in aerial plant parts collected from different populations. Chromatographic separations were achieved by a UPLC BEH C18 column, PDA detector and a water/acetonitrile gradient as a mobile phase. Sutherlandioside B eluted at 15.02 min on a positive ionization mode with a base peak mass of 473 m/z and a UV spectra of 236nm, whereas sutherlandioside B analogues, sutherlandiosides A, C and D eluted at 18.54, 17.96, 18.70 min with base peak masses of 635, 489 and 635 m/z respectively. Chemometric-based cluster analysis separated populations into different chemical lineages based on sutherlandioside B and its analogues with principal component analysis revealing four distinct clusters. The samples containing sutherlandioside B were the plants growing in semi-arid areas of the Karoo region while this compound was virtually not detected in plants growing in the coastal Gansbaai region with contrasting geoclimatic characteristics to the Karoo. Although synthesis of sutherlandioside B is likely influenced by environmental factors, the possible impact of genetic differentiation cannot be dismissed.

Acknowledgements: National Research Foundation South Africa is acknowledged for research funding and Central Analytical Facility (Stellenbosch University) is thanked for sample analyses.

Keywords: Sutherlandia frutescens, sutherlandiosides, metabolomics, LC-MS, chemometrics.

References:

[1] Stander BA, Marais S, Steynberg TJ, Theron D, Joubert F, Albrecht C, Joubert AM. Influence of Sutherlandia frutescens extracts on cell numbers, morphology and gene expression in MCF-7 cells. J Ethnopharmcol 2007; 112: 312 – 318

[2] Van Wyk, BE, Van Oudtshoorn B, Gericke N. Medicinal plants of South Africa. Second Improved Impression, 2000. Briza Publications. Pretoria, South Africa.