Development of standard operating protocol for slide preparation of powdered bark samples with varying grinding techniques

Abstract

Background: Powder microscopy is the most common method to authenticate herbal drugs. The botanical origin and quality can be determined based on cellular features. Objective: To develop a standard operating protocol to prepare slides of powdered bark samples obtained by using different grinding techniques. Materials and methods: Alstonia scholaris, Saraca asoca, Syzygium cumini, Terminalia arjuna and Pongamia pinnata were selected for study. Three samples of each bark were studied: Sample A was collected from NISCAIR Pusa, New Delhi. Sample B and C were procured from industries and were coded as: AP I, AP II, AP III, AP IV and AP V and MP I, MP II, MP III, MP IV and MP V respectively. The slides were prepared by soaking and chemical treatment and photographed by Motic microscope. The samples were observed for general and specific features of the bark and the impact of grinding (industrial grinding and blade grinding in laboratory) on probability of change in various microscopical features. Results: The microscopical features were found to be stable and specific, which can be used to determine the botanical identity of the drug. There was no significant difference in microscopical characters of powdered barks which emphasized that grinding technique does not have any impact on powder microscopy of different bark samples. The method of preparation of slide was also optimized. Conclusion: Powder microscopy, irrespective of grinding technique can be used as a cheap, fast, efficient and accurate method to authenticate herbs or distinguishing species with similar morphological characters without cutting and examining sections.