A review on saponins from medicinal plants: chemistry, isolation, and determination

Abstract

It has been estimated that out of 4,22,000 flowering plants reported from the world, more than 50,000 are used for medicinal purposed.1 Since ancient times, bioactive medicinal plants are used in traditional or folk medicine for the treatment of various diseases. Recently using of phytochemicals is considered to be safer and congenial to the biology of the human body. Medicinal plants are the main source for the preparation and extraction of various modern drugs and pharmaceuticals like saponins. Signs of progress of Phytochemistry have been supported enormously by the rapid development and accumulation of chemical methods of screening of various medicinal plants for particular biochemical usage. The pharmaceutical and medicinal values of the applied medicinal plants are in the bioactive phytochemical constituents that produce specific physiological action on the human body. Some of the most important bioactive constituents are saponins, flavonoids, and alkaloids. Triterpenoid saponins are surface active glycosides of triterpenes that possess a wide, biologically active group of terpenoids and include a large chemical diversity of secondary metabolites with more than different 100 carbon skeletons identified from terrestrial, marine living organisms, and medicinal plants.2 Triterpenoids as a saponin have its own characteristics like cause hemolysis of red blood cells (RBC’s), form persistent froth if shaken with water, and it is soluble in water, alcohol and a mixture of both. These naturally occurring compounds form the backbone of modern medicine or drugs. Saponins are a class of bioorganic compounds found in particular abundance in the plant kingdom. More specifically, they are naturally occurring glycosides described by the soap-like foaming, and consequently, they produce foams when shaken in aqueous solutions. Structurally saponins are having one or more hydrophilic glycoside sugar moieties combined with a lipophilic triterpene molecule.3 Literature shows that saponins exhibit a biological role and medicinal properties such as hemolytic factor4 anti-inflammatory,5 antibacterial,6 antifungal,7 antiviral,8 insecticidal9, anticancer,10 cytotoxic11 and molluscicidal action.12 In addition, saponins are reported to exhibit cholesterol-lowering action in animals and human.13,14 Waheed et al.15 isolated a novel steroidal saponin glycoside from Fagonia indica that can induce cell-selective apoptosis or necrosis in cancer cells. Saponins were considered as a starting precursor for the semi-synthesis of steroidal drugs in the pharmaceutical industry. Sheng et al.16 reviewed the clinical significance of triterpenoid saponins in the prevention and treatment of metabolic and vascular disease. The above medicinal researches and applications reflect the increasing of the interest of saponins as a bionatural source material, but understanding of the relationship between the chemistry of saponins and its medical action is not easy task for many chemists, physicians, and researchers. Due to the complexity, importance, and interferences of the chemistry of saponin, the main purpose of this review article is giving detailed information about (1) the classification of saponin, (2) the chemical structure of various types of saponins and its functional groups, (3) examples for mono and didesmosidic triterpenoid saponins, (4) ordinary and soxhlet extraction methods in the laboratory, and finally (5) qualitative, and quantitative determination of saponins.