Objectives Barleria, a large genus of the Acanthaceae family, comprises more than 300 species with diverse taxonomy, cytogenetics, phytochemistry and pharmacological potential. Therefore, the aim of this review is to critically assess the research on Barleria and provide guidance for future investigations. Methods The data were obtained from different sources, such as books, theses, journals and some of the websites and internet-based searches, published from 1901 to 2020. Data obtained from PubMed, Google Scholar, ScienceDirect, online electronic journals, SpringerLink, Wiley, etc. have also been used. Key findings The species of this genus exhibit considerable medicinal properties. Cytogenetical data are scantily available with chromosome counts available for only 24 species. The most common chromosome number is 2n = 2x = 40. So far, 187 compounds are reported from Barleria species. The active principles, their uses, toxicity and pharmacological effects are discussed. Essential oils, flavones, flavonoids, glycosides, terpenes and terpenoids form the major compounds. Summary It is highly recommended that the pharmacological and economic potential of Barleria species should be exploited and more detailed studies and attention be geared towards its utilization and conservation. In addition, to ensure maximum pharmacological benefits and sustainable use, it is necessary to have empirical information explaining its ethnobotanical values as well as commercial potential.

Nomenclatural investigation was carried out on eight binomials published in the genus Barleria L. (Acanthaceae). All the binomials were typified. Six of these names (B. cuspidata Heyne ex Nees, B. grandiflora Dalzell, B. lawii T.Anderson, B. nitida Nees, B. pilosa Heyne ex Nees and B. strigosa Willd. are currently accepted names. Of the remaining two, B. hirsuta Nees is a later homonym of B. hirsuta Jacq. and B. polytricha Wall., a synonym of B. strigosa Willd.

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Barleria cristata L., commonly known as the Philippine violet, is native to South Asia. It is an ornamental plant and is also used for the treatment of a variety of diseases. In India, it is found throughout the country in many forms, varying in its floral attributes (calyx and corolla) and habitat. In order to understand the species limits in B. cristata, we studied morphological as well as palynological variation and assessed the phylogenetic relationships among five different morphotypes. The studied morphotypes (populations) came from three phytogeographical regions, namely the Western Ghats, the Deccan Peninsula and the Western Himalaya. The naturally occurring populations from the Deccan Peninsula and the Western Himalaya showed conspicuous differences in their morphology. All the morphotypes had oblate spheroidal, tri-brevicolporate and honey-combed pollen grains which differed only in their quantitative parameters. The distinct-looking morphotypes, namely, Nandi Hills, Uttarakhand and cultivated morphotypes, could not be separated based on pollen characters. Phylogenetic analyses based on chloroplast DNA sequences revealed that our samples formed a clade sister to the B. cristata specimen used in the previous study. The genetic variation within morphotypes was not enough for the genomic regions investigated; however, it revealed among morphotype genealogies in detail. Phylogenetic analyses showed that there were three monophyletic groups within the B. cristata complex that exhibited some morphological differences. Nevertheless, based on the present sampling, it is not possible to delimit these morphotypes at specific or infraspecific level. To reach such conclusions, further investigations like sampling this species across its distribution range in India and assessment of intraspecific relationships, and their cytogenetical characterization should be done.