The secretory scales of Combretum erythrophyllum (Combretaceae): Micromorphology, ultrastructure and histochemistry

Abstract

Combretaceae is a large medicinal family prevalent on the African continent. Traditional healers commonly utilize species of this family to treat or cure a wide array of illnesses and diseases. Medicinal flora are known to contain secondary metabolites which may effectively improve an individual's state of health. These medicinal properties are attributed to secondary metabolites, which in some instances, are exuded by specialized secretory structures, such as trichomes, laticifers or glands. This study investigated the micromorphology, ultrastructure and histochemistry of the secretory structures found on the surface of leaves (emergent, young and mature) and stems of Combretum erythrophyllum. The micromorphological analysis identified two distinct trichome types, peltate scales and non-glandular trichomes. The head cell count of peltate scales appeared to increase upon leaf maturation and ranged from 8 to 19 cells. In addition, the granulocrine pathway was identified as a possible mode of secretion due to the extensive presence of vesicles, vacuoles and electron dense material within the peltate scales. Preliminary histochemical analyses indicated the predominant presence of alkaloids, phenolic compounds and essential oils within the exudate. Medicinally, these metabolites are known to exhibit anti-oxidant, anti-inflammatory properties and anti-microbial properties. In accordance, these beneficial compounds may be further developed for use in medicinal applications.