Medicinal Powders from Neem Leaves, Bark and Seeds: A Review of Preparation and Evaluation

Medicinal powders (churna) are the oldest and simplest herbal dosage forms, in which the dried drug is reduced to a fine powder, sieved and packed. Neem (Azadirachta indica) is one of the most widely used medicinal trees of India, and its leaf, bark and seed are the parts most commonly used. These parts differ in their structure and chemical composition: the leaf is rich in flavonoids and phenolic acids, the bark in tannins and calcium oxalate crystals, and the seed kernel in fixed oil, protein and fibre, so each has to be powdered and standardised separately. Neem powders in the market are often not standardised. The present review discusses medicinal powders as a dosage form, their advantages and limitations, the profile of the neem leaf, bark and seed, the method of preparation of powders by drying, grinding and sieving through sieve no. 85, the tests used for standardisation and evaluation, including flow properties, ash and extractive values, phytochemical screening, TLC fingerprinting, microbial load and stability, and the important reports on the subject. The review shows that controlled preparation and evaluation are needed to obtain reproducible, standardised neem powders.