Two new PhD graduates from ACDB

Two new PhD graduates from ACDB

Congratulations to Drs Dorcas Olaniyan and Estherna Pretorius, who graduated with PhDs at UJ on 19th May 2022.

Dorcas & Estherna

For her doctoral study, Dorcas has successfully unravelled the complicated relationships among the species of saffron bushes in the stringbark family Thymelaeaceae. Southern Africa is the center of diversity for this group of shrubs, comprising over 200 species. The circumscription of the core genus, Gnidia, has been especially problematical. Building on previous evolutionary studies, Dorcas has at last provided a clear analysis of the situation, using the latest molecular phylogenetic techniques. Her phylogenetic analysis of four plastids and one nuclear gene region shows conclusively that the problem genus Gnidia comprises several distinct groups of species. Using this knowledge, she has provided the first evidence-based classification for the saffron bushes. This is an essential step in improving our understanding of the group of plants, several of which are of economic and cultural significance.

Estherna investigated the utility of DNA barcoding and phytochemical profiling techniques to authenticate herbal products – specifically those claimed to contain medicinally relevant species of Harpagophytum and Agathosma. Following the development of taxon-specific reference DNA barcode libraries as well as chemical profiles, a market survey was conducted utilizing these tools to authenticate Harpagphytum- and Agathosma-containing commercial herbal products. Results indicated that 76% of the devil’s claw products and 20% of the buchu products tested were substituted with inferior species. Increased substitution can be seen worldwide, and Estherna's study reiterates that South Africa is not exempted from this trend. The created reference DNA barcode libraries and chemical profiles can serve as the first step in the authentication of raw material before processing begins to assist quality control measures within the herbal industry.

Written by Michelle van der Bank