Investigating the effect of varying temperatures on the phytochemical constituents of medicinal plants found in the Maltese Islands

Abstract

Herbal medicine has recently gained a renewed interest, which has given rise to a demand for further information to accentuate their effects and ensure a prolonged shelf-life. The provision of this quality of information has been rendered as critical by the World Health Organisation, due to the availability and accessibility of the raw materials worldwide. This research aimed at studying the effect of varying storage temperatures on the polyphenolic content of Chiliadenus bocconei Brullo, Mentha spicata L., Ocimum basilicum L. and Petroselinum crispum (Mill.) Fuss. The employed methodology makes use of the Folin-Ciocalteu test as a means to determine an approximate shelf life via accelerated stability testing of the total phenolic content. The findings indicate higher preservation of the total phenolic content at lower temperatures, with stable trends visible until a maximum of 30°C. The resulting data indicated increased stability within the plant matrix of the Chiliadenus Bocconei Brullo, while for Mentha spicata L., the extracts presented higher stability. Basil extracts presented similar outcomes, however samples kept at room temperature exhibited increased consistency. The same outcome was also observed for the Parsley plant material. The UV-Vis profile was measured in order to assess long-term stability by analysing the anthocyanin content within the species under study. The anthocyanin content provided inconclusive results, however further insight on the behaviour of anthocyanins at different temperatures was observed. Higher stability of the anthocyanin content was observed within the plant matrices, when compared to the plant extracts. Both phases of the method outputted relevant information about the behaviour of different plant matrices with relation to polyphenolic preservation. Further studies may be required to further consolidate the obtained results and identify herb-specific metabolites as markers of shelf-life and stability.