Pharmacognostic Quality Parameters (Physicochemical Evaluation)

A defined set of pharmacognostic physicochemical parameters, specified in the Indian Pharmacopoeia and WHO quality control guidance, provides the foundational quality assessment applied to every crude herbal drug prior to further processing. Foreign matter determination, performed by visual inspection and sieving, quantifies contamination by insects, soil, or non-target plant parts and must remain below the limit stated in the relevant pharmacopoeial monograph. Loss on drying, determined by oven-drying at 105°C to constant weight (or by Karl Fischer titration for moisture-sensitive material), quantifies residual moisture content, conventionally required to remain below approximately ten percent for most powdered herbal drugs, since excessive moisture promotes microbial growth and constituent degradation during storage. Total ash, obtained by incineration at 600°C, quantifies the total inorganic residue and serves as an indirect indicator of soil or mineral adulteration; acid-insoluble ash, obtained by boiling the total ash residue with dilute hydrochloric acid and incinerating the remaining filtrate, specifically indicates sand or silica contamination and is conventionally limited to below two percent for most drugs; and water-soluble ash, obtained by subtracting the water-insoluble residue from total ash, indicates the water-soluble mineral content of the drug. Water-soluble and alcohol-soluble extractive values, determined by cold maceration of a defined quantity of powdered drug in water or ninety percent ethanol respectively followed by evaporation and weighing, provide a rapid indirect estimate of the overall extractable constituent content and are among the most widely cited quality parameters in official pharmacopoeial monographs. Crude fibre content, determined by sequential acid and alkali digestion, indicates the cellulose and lignin content of the drug and is of particular relevance to bulking and adulteration assessment.