Plant species belonging to the family Acanthaceae are globally known to possess various medicinal properties and have cultural and economic importance in both traditional medicine and horticulture. They are important to both animals and humans and are used as food or for ornamental purposes worldwide. Barleria is the third largest genus in the family Acanthaceae. A few of the highly important and reported species of Barleria include B. prionitis, B. cristata, B. grandiflora, and B. lupulina. The flowers, leaves, stems, roots, and seed extracts of plants belonging to this genus are rich in bioactive compounds and have exhibited significant medicinal potential for the treatment of various ailments and infections. Evidence derived from several studies has demonstrated the antioxidant, antibacterial, antifungal, anti-inflammatory, anticancer, antidiabetic, antiulcer, hepatoprotective, analgesic, antiamoebic, antihelminthic, antiarthritic, antihypertensive, antiviral properties and toxicity of extracts, in addition inhibition of acetylcholinesterase activity and biosynthesis of nanoparticles, of the plant and seed extracts of species belonging to Barleria. Studies have reported that bioactive compounds such as flavonoids, quinones, iridoids, phenylethanoid glycosides, the immunostimulant protein “Sankaranin”, and antibiotics isolated from Barleria species are resposnsible for the above biological activities. Traditionally, the genus Barleria has significant medicinal potential; however, there is a scarcity of information on various species that are yet to be evaluated. This review provides a comprehensive report on existing literature, concerning the phytochemistry and biological activities of the genus Barleria.

Leucas lavandulaefolia Sm. (Lamiaceae) is an important medicinal plant with a broad spectrum of pharmacological activities. This study aimed at characterizing the morphology, distribution, and chemical composition of the secretions of trichomes at different developmental stages on the leaves of L. lavandulaefolia, using light and electron microscopy. Morphological observations revealed the presence of bicellular non-glandular, glandular peltate, and capitate trichomes on both adaxial and abaxial leaf surfaces. The density of both non-glandular and glandular trichomes decreased with the progression of leaf development. Heads of peltate and short-stalked capitate trichomes were between 20.78–42.80 µm and 14.98–18.93 µm at different developmental stages. Furthermore, long-stalked capitate trichomes were rare and infrequent. Leaf sections revealed the presence of important secondary metabolites in glandular trichomes, i.e., terpenoids. This study represents the first report on the morphology and histochemistry of trichomes of L. lavandulaefolia; therefore, there is a great scope for further research in this field.

Barleria albostellata (Acanthaceae) is a shrub located in South Africa and is relatively understudied. However, plants within this genus are well known for their medicinal and ethnopharmacological properties. This study aimed to characterise the phytochemical compounds and antibacterial efficacies of B. albostellata. Phytochemical analysis, fluorescence microscopy and gas chromatography-mass spectrometry (GC-MS) analysis were performed to determine the composition of compounds that may be of medicinal importance. Crude leaf and stem extracts (hexane, chloroform and methanol) were subjected to an antibacterial analysis against several pathogenic microorganisms. The qualitative phytochemical screening of leaf and stem extracts revealed the presence various compounds. Fluorescence microscopy qualitatively assessed the leaf and stem powdered material, which displayed various colours under bright and UV light. GC-MS chromatograms represents 10–108 peaks of various compounds detected in the leaf and stem crude extracts. Major pharmacologically active compounds found in the extracts were alpha-amyrin, flavone, phenol, phytol, phytol acetate, squalene and stigmasterol. Crude extracts positively inhibited Gram-positive and Gram-negative bacteria. Significance was established at p < 0.05 for all concentrations and treatments. These results indicate that the leaves and stems of B. albostellata are rich in bioactive compounds, which could be a potential source of antibacterial agents for treating various diseases linked to the pathogenic bacteria studied. Future discoveries from this plant could advance the use of indigenous traditional medicine and provide novel drug leads.

Barleria albostellata C.B. Clarke (Acanthaceae) is a plant native to South Africa and relatively few studies have been performed on it. Species in this genus are known for their ethnopharmacological and phyto-medicinal values. In this study, the total flavonoid and phenolic contents and the antioxidant and cytotoxic activities of hexane, chloroform, and methanol extracts were evaluated at five different concentrations (15, 30, 60, 120, and 240 μg/mL). The antioxidant activity of the extracts of B. albostellata was assessed in vitro using the 2,2′-diphenyl-1-picrylhydrazyl (DPPH) scavenging and ferric reducing antioxidant power (FRAP) assays, while the phenolic content was determined using a Folin–Ciocalteu assay. The extracts’ cytotoxicity was established using a 3-[(4,5-dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide] (MTT) assay in human embryonic kidney (HEK293), cervical cancer (HeLa), and breast adenocarcinoma (MCF-7) cell lines. Methanolic leaf extracts had the highest total flavonoid content (42.39 ± 1.14 mg GAE/g DW) compared to other solvents. Additionally, the total phenolic content was the greatest in the methanol leaf extract (6.05 ± 0.09 GAE/g DW), followed by the methanol stem extracts (2.93 ± 0.73 GAE/g DW). The methanolic leaf and stem extract concentrations needed for 50% inhibition (DPPH) were 16.95 µg/mL and 14.27 µg/mL, respectively, whereas for FRAP, the reducing powers of all extracts were considerably lower than the ascorbic acid standard. The IC₅₀ values of extracts tested in the three cell lines were >63 µg/mL. According to the findings of our study, the leaves and stems of B. albostellata are rich in several bioactive compounds that may be a possible source of natural antioxidants and may have the potential to treat certain diseases. The extraction of the bioactive compounds from the leaves and stems of B. albostellata using bioassay-guided fractionation and the assessment of their safety will be essential for further investigations into this species in the search of potential novel therapeutic drug leads. To the best of our knowledge, this is the first report of the cytotoxic activities of leaf and stem extracts of Barleria albostellata.

Silver nanoparticles (AgNPs) have increasingly gained attention owing to their distinctive physicochemical and biological properties. The objective of the investigation was to biologically synthesize AgNPs using plant extracts from Barleria albostellata. The synthesized AgNPs, obtained from B. albostellata (leaves and stems), were characterized through various techniques including UV-visible spectroscopy, scanning electron microscopy (SEM), high-resolution transmission electron microscopy (HRTEM), energy-dispersive X-ray analysis, Fourier transform infrared (FTIR) spectral analysis, and nanoparticle tracking analysis (NTA). The antibacterial efficacy of the synthesized AgNPs was evaluated utilizing the disk diffusion method. The cytotoxicity effects of the synthesized AgNPs were determined using the MTT assay (3-[(4,5-dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide]) in cervical cancer (HeLa), embryonic kidney (HEK293), and breast adenocarcinoma (MCF-7) cell lines. The results indicate that B. albostellata extracts could serve as eco-friendly biofactories for the synthesis of AgNPs. UV-vis spectroscopy of the leaf and stem extracts revealed absorption peaks within the range of 400–450 nm, thereby confirming the synthesis of AgNPs. Elemental Ag was highest in the methanol leaf extracts (16.87 ± 0.89%) and lowest in the powdered stem extracts (7.13 ± 1.44%). Synthesized AgNPs were predominantly spherical in shape. HRTEM revealed that synthesized AgNPs from the methanolic stem extracts (34.32 ± 16.99 nm) were larger in size, while those from the powdered stem extracts were smaller (16.57 ± 5.55 nm). AgNPs synthesized from both the leaf and stem extracts exhibited zeta potential values between −8.8 and −32.1 mV, with hydrodynamics diameters ranging from 34.3 to 111.3 nm. FTIR spectroscopy confirmed the presence of various functional groups on the AgNPs. AgNPs synthesized from the leaf and stem extracts displayed significant antibacterial activity and were sensitive to Gram-negative and Gram-positive bacteria. AgNPs exhibited significant antibacterial activity (diameter of the zone of inhibition) against Pseudomonas aeruginosa (21.67 ± 2.87 mm) in the leaf methanolic extract. Synthesized AgNPs exhibited selective in vitro cytotoxicity against HEK293, HeLa, and MCF-7 cell lines. The IC₅₀ values of the AgNPs synthesized from the various extracts were all above 9 µg/mL. Significant cytotoxic levels (IC50 16.11 and 27.23 µg/mL) were observed for the MCF-7 cell line upon exposure to the methanolic leaf and stem AgNPs. This study recommends the use of medicinal plant extracts in producing economically effective AgNPs, due to their efficient capping. Overall, AgNPs synthesized from B. albostellata extracts comprised novel antibacterial and anticancer agents, and warrant further investigation. Bio-synthesized AgNPs show great potential in the area of nanotechnology and may be used as an affordable, eco-friendly alternative for the delivery of conventional therapeutics.

Barleria albostellata C.B. Clarke (grey barleria, Acanthaceae) is an indigenous shrub to South Africa and has been relatively understudied. This shrub is a valuable medicinal plant with a wide spectrum of antibacterial and anti-inflammatory activities. Detailed studies on the floral and pollen morphology on B. albostellata are rare. This study was conducted to observe the morphology of the flower and pollen grains using stereomicroscopy and scanning electron microscopy (SEM). Morphological observations showed numerous non-glandular trichomes on the bracteoles and bracts of B. albostellata. Three types of trichomes were identified on these structures: I—unicellular, II—multangulate-dendritic branched non-glandular trichomes, and III—capitate glandular trichomes. A taxonomical description of the floral structures using stereo and SEM micrographs is provided. SEM micrographs revealed the pollen grains as globose tricolporate with a rough honeycomb exine, and small granules inside the lumina. The diameter of the pollen grains was 77.53 ± 5.63 μm, whereas the aperture of these grains was 14.31 ± 0.59 µm. This study provides insight into the floral biology of B. albostellata, and the results presented here will add to the body of knowledge and encourage further research on this species.