Comparative study of three Plumbago L. species (Plumbaginaceae) by microscopy, UPLC-UV and HPTLC

Ahmed M. Galal, Vijayasankar Raman, Bharathi Avula, Yan-Hong Wang, Chidananda Swamy Rumalla, Aruna Dharmapriya Weerasooriya, Ikhlas A. Khan

This paper presents a comparative study of anatomy of leaves, stems and roots of three species of Plumbago, namely P. auriculata Lam., P. indica L. and P. zeylanica L. by light microscopy. The paper also provides qualitative and quantitative analysis of the naphthoquinone, plumbagin-a major constituent present in these species-using UPLC-UV. Microscopic examinations revealed the presence of distinctive differences in the anatomical features of the leaf, stem and root of the three species, and these can thus be used for identification and authentication of these species. UPLC-UV analysis showed the highest concentration of plumbagin in the roots of P. zeylanica (1.62% w/w) followed by the roots of P. indica (0.97% w/w) and then P. auriculata (0.33-0.53% w/w). In contrast, plumbagin was not detected in the stems and leaves of P. indica and in the leaves of P. auriculata, whereas very low concentrations (<0.02% w/w) of plumbagin were detected in the stems and leaves of P. zeylanica and in the stems of P. auriculata. HPTLC fingerprints of the leaf and root of the three species exhibited distinguishable profiles, while those of the stems were undifferentiated.