ABSTRACT
Objective: To study detailed Pharmacognosy of the bark of Nyctanthes arbortristis Linn (Oleaceae), an important plant in Indian system of medicine. Methods: the macroscopy, microscopy, physicochemical analysis, preliminary phytochemical testing of powder of the plant bark and other WHO recommended methods for the standardization was done. Results: Trunk bark consists of two distinct regions i.e. outer bark and inner bark. Outer bark consists of broad periderm of a wide phellem and inner phelloderm regions. Inner bark is broader than the outer part and it includes all the secondary phloem tissues. It can be distinguished into 2 zones viz. collapsed secondary phloem and non-collapsed secondary phloem regions. Collapsed secondary phloem region consist of thick blocks of phloem sclereids and radially oblique dark streaks of crushed sieve tubes and dilated axial parenchyma cells. Non-collapsed secondary phloem region is the conducting part of the phloem where the sieve elements are intact. It consists of intact sieve tube members, companion cells, axial parenchyma cells and narrow undilated ray. Calcium oxalate crystals are abundant in collapsed phloem region. Conclusions: it can be concluded that the pharmacognostic profile of N. arbortristis bark is helpful in developing standards for quality, purity and sample identification.