Characterization of Syzygium travancoricum Gamble (Myrtaceae), a critically endangered endemic species of Kerala

Abstract

The objective of this research was to conduct a comprehensive investigation of Syzygium travancoricum Gamble (Myrtaceae), an endemic and endangered species of Kerala. In addition, another goal was to provide a taxonomic resolution to the ambiguities regarding the identity of this species due to its close resemblance to other species, S. stocksii. The study also aimed to evaluate the medicinal properties of this species. For this, various analytical techniques such as morphological, anatomical, histochemical, phytochemical, molecular and pharmacological methods were used. The study focused on morphologically closely related populations of S. travancoricum spread across five districts in Kerala. The morphological and anatomical studies revealed that populations collected from Pookode and Paliyeri Mookambika Kavu showed unique morphological and anatomical characteristics distinct from S. travancoricum and were closely related to S. stocksii. Histochemical analysis revealed the presence of tannins, lignin, starch and essential oils in various parts of S. travancoricum. Using the results of morphological and anatomical studies, the UPGMA phylogram of S. travancoricum showed that the plants found in Pookode and Palyeri Mookambika Kavu are closely related to S. stocksii and have diverged into a separate clade. Phytochemical analysis of S. travancoricum leaf and bark extracts revealed the presence of alkaloids, flavonoids, saponins, tannins, steroids, phenols and terpenoids. Moreover, the extracts of S. travancoricum contained high levels of phenolic compounds (240.2 mg GAE/g)and flavonoids. Apart from this, the presence of vitamins, minerals, phenols, anthocyanins, carbohydrates, potassium and calcium was also found in their fruits. The essential oil GC-MS profiling identified that the leaves of S. travancoricum are rich in monoterpenoids and sesquiterpenoid compounds such as β-caryophyllene, caryophyllene epoxide, β-geraniol, α-farnesene, and α-selinene, monoterpenoids such as α-pinene, β-pinene, ocimene isomers, myrcene, limonene and terpineol. The Bayesian phylogenetic tree based on the concatenated dataset revealed paraphyletic relationships between two species, S. travancoricum and S. stocksii. Also, it supported the distinction of S. travancoricum as a distinct species from S. stocksii. The essential oil of the leaves of S. travancoricum effectively prevented the growth of different bacterial and fungal strains. Moreover, the study found that the leaves and bark of this plant are reservoirs of antioxidants, and their aromatic oil and extracts have the potential to work effectively against arthritis, inflammation and diabetes. As part of this study, about 200 trees were conserved through ex situ conservation strategies implemented by establishing green spaces in five grama panchayats of Thrissur, Palakkad and Pathanamthitta in Kerala.