1.4.2 Microscopic Authentication (Histological Evaluation)

Microscopic authentication examines the internal cellular architecture of the plant tissue, providing diagnostic detail that survives even when a sample has...

Microscopic authentication examines the internal cellular architecture of the plant tissue, providing diagnostic detail that survives even when a sample has been powdered or is otherwise not amenable to macroscopic assessment. Transverse-section staining, typically using safranin (which stains lignified cell walls red) combined with fast green (which stains cellulose green) and occasionally haematoxylin, reveals diagnostic anatomical features including vascular bundle arrangement, the palisade-to-spongy mesophyll ratio (the dorsoventral index used to characterise leaf drugs), and the distribution of calcium oxalate crystals. Powder microscopy, performed on material ground to pass a #60 mesh sieve, allows identification of characteristic elements such as stomatal type (rubiaceous, paracytic, or anisocytic), fibre morphology, and starch grain shape, and is formally codified in the Indian Pharmacopoeia's microscopic monographs and in the WHO Monographs on Selected Medicinal Plants.