The pharmacognostic value of leaf and stem anatomy in rooibos tea (Aspalathus linearis)

Abstract

Aspalathus linearis (Fabaceae) is an exceptionally polymorphic species comprising seven distinct infraspecific forms, some reseeding and some resprouting after fire. We present, for the first time, anatomical data to describe the stems and leaves that are used to produce the well-known herbal product, rooibos tea. Comparisons between the commercial (cultivated) red tea type and selected wild types showed limited anatomical variation within the species. The cut and fermented leaves of the commercial form and various wild forms of the species show considerable variation, ranging from reddish brown to various shades of brown, grey and black. Infusions or decoctions are less variable and are bright reddish brown. Characters that may be useful for pharmacognostic purposes are the terete leaf segments, the similarity between leaf and stem sections, the thick cuticle, the bright yellowish brown colour of the epidermal cells (of leaves and young stems), the anomocytic stomata, the ring of small vascular bundles in the leaf and the highly sclerified main vascular bundle of the leaf.