The study of medicines derived from natural sources.
The word "pharmacognosy " is derived from the Greek words φάρμακον pharmakon (drug), and γνῶσις gnosis (knowledge).
It is defined as pharmacognosy as "
The study of the physical, chemical, biochemical and biological properties of drugs, drug substances or potential drugs or drug substances of natural origin as well as the search for new drugs from natural sources"
. It is also defined as the study of crude drugs. OR
"The study of natural product molecules (typically secondary metabolites) that are useful for their medicinal, ecological, gustatory, or other functional properties.
During 19th and the beginning of the 20th century—"pharmacognosy" was used to define the branch of medicine or commodity sciences which deals with drugs in their crude, or unprepared, form. Crude drugs are the dried, unprepared material of plant, animal or mineral origin, used for medicine.
As late as the beginning of the 20th century, the subject had developed mainly on the botanical side, being particularly concerned with the description and identification of drugs both in their whole state and in powder form. Such branches of pharmacognosy are still of fundamental importance, particularly for pharmacopoeial identification and quality control purposes, but rapid development in other areas has enormously expanded the subject.
Although most pharmacognostic studies focus on plants and medicines derived from plants, other types of organisms are also regarded as pharmacognostically interesting, in particular, various types of microbes (bacteria, fungi, etc.), and, recently, various marine organisms.
Fields under Pharmacognosy:
Medical ethnobotany: the study of the traditional use of plants for medicinal purposes;
Ethnopharmacology: the study of the pharmacological qualities of traditional medicinal substances;
Phytotherapy: the medicinal use of plant extracts
Phytochemistry: the study of chemicals derived from plants (including the identification of new drug candidates derived from plant sources).
Zoopharmacognosy: the process by which animals self-medicate, by selecting and using plants, soils, and insects to treat and prevent disease.
Marine pharmacognosy: the study of chemicals derived from marine organisms.
http://microamaze.blogspot.in/2016/01/pharmacognosy.html