Phytochemical profiling and chemotypic variation study of Lobostemon fruticosus (L.) H.Buek

• Lobostemon fruticosus exhibited conserved phytochemical profiles in samples from eight populations ( n = 24). • Eight compounds were tentatively identified in the aqueous methanolic extract. • Chemometric analysis revealed quantitative chemotypic variation between samples. • Pyrrolizidine alkaloids were detected concentration range of 53 mg/kg-169 mg/kg. Lobostemon fruticosus (L.) H.Buek belonging to Boraginaceae family, is an evergreen and woody shrub that grows in the Cape region of South Africa. The twigs and leaves of the plant have been traditionally used by the Khoisan to treat various ailments. A tea prepared from the leaves is consumed in the morning to treat ringworm. Other preparations are made to treat several dermatological conditions including burns, wounds, ulcers, syphilis, ringworm, erysipelas and eczema. Although biological activities have been reported for the plant, there are limited studies on the phytochemical profiling and chemotypic variation of the plants collected from different locations, which may have an effect on the efficacy of the plant. The aim of this study was to perform phytochemical profiling of L. fruticosus from different populations and determine chemotypic variation using a chemometrics approach. Aqueous methanolic extracts (80 %) of the aerial parts of L. fruticosus were prepared from 24 samples collected from eight locations in the Western Cape Province. Chemical profiles were determined using high-performance thin layer chromatography (HPTLC) and ultra-performance liquid chromatography coupled to a mass spectrometer (UPLC-MS). SIMCA-P 14+® was used to perform chemometric modelling, including principal component analysis (PCA), hierarchical cluster analysis (HCA) and orthogonal projections to latent structures-discriminant analysis (OPLS-DA). High-performance thin layer chromatographic (HPTLC) profiles of L. fruticosus from various locations exhibited a high level of similarity. However, the band intensities exhibited variation between samples, indicating that some of the compounds differed quantitatively. Eight compounds were tentatively identified as globoidnan B, rutin, rabdosiin, rosmarinic acid, globoidnan A, sagerinic acid, 3,4,5-trihydroxy-6-[5‑hydroxy-2-(4‑hydroxy-3-methoxyphenyl)-3‑methoxy-4-oxochromen-7-yl] oxyoxane-2-carboxylic acid and isolariciresinol 9- O -β-d-glucoside. Chemometric analysis of the UPLC-MS data revealed quantitative chemotypic variation among L. fruticosus samples that was location specific, and three chemotypes. Pyrrolizidine alkaloids were found to be present in all the populations at a concentration range of 53–169 mg/kg and this raises a potential hepatoxicity concern for oral preparations. In line with the traditional uses of L. fruticosus, future research should focus on permeability studies and establishing safety limits for topical and oral preparations.