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The organogenic potential and antioxidant potential (1, 1-diphenyl-2-picrylhydrazyl-scavenging activity) of the medicinal plant Piper nigrum L. (black pepper) were investigated. Callus induction and shoot regeneration were induced from leaf explants of potted plants cultured on MS medium supplemented with different plant growth regulators. The best callogenic response was observed on explants cultured for 30 days on MS medium supplemented with either 0.5 or 1.5 mg l -1 6-benzyladenine (BA) ? 1.0 mg l -1 a-naphthaleneacetic acid. Subsequent transfer of the callogenic explants onto MS medium supplemented with 1.5 mg l -1 BA ? 1.0 mg l -1 gibberellic acid (GA 3 ) achieved 85% shoot organogenesis after 30 days of culture. The maximum number (7.2) of shoots/explant was recorded for explants cultured in MS medium supplemented with 1.0 mg l -1 BA. Following the transfer of shoots to an elongation medium, the longest shoots (5.4 cm) were observed on MS medium supplemented with 1.0 mg l -1 BA ? 1.0 mg l -1 GA 3 . The elongated shoots were rooted on MS medium supplemented with different concentrations of indole butyric acid. An assay of the antioxidant potential of the in vitro-grown tissues revealed that the antioxidant activity of the regenerated shoots was significantly higher than that of callus and the regenerated plantlets.

Prunella vulgaris L. (P. vulgaris) is an important medicinal plant with a wide range of antiviral properties. Traditionally, it is known as self-heal because of its faster effects on wound healing. It is commonly known as a natural antiseptic due to the presence of various polyphenols. There is lack of research efforts on its propagation and production of bioactive compounds under field and in vitro conditions. In this study, the effects of different ratios (1:2, 1:3, 2:1, and 3:1) of silver (Ag) and gold (Au) nanoparticles (NPs) alone or in combination with naphthalene acetic acid (NAA) were investigated for callus culture development and production of secondary metabolites. The Ag (30 μg l), AgAu (1:2), and AgAu (2:1) NPs in combination with NAA (2.0 mg l) enhanced callus proliferation (100 %) as compared to the control (95 %). Among the different NPs tested, AuNPs with or without NAA produced higher biomass in log phases (35-42 days) of growth kinetics. Furthermore, AgAu (1:3) and AuNPs alone enhanced total protein content (855 μg-BSAE/mg-fresh weight (FW)), superoxide dismutase (0.54 nM/min/mg-FW), and peroxidase (0.39 nM/min/mg-FW) enzymes in callus cultures. The AgAuNPs (1:3) in combination with NAA induced maximum accumulation of phenolics (TPC 9.57 mg/g-dry weight (DW)) and flavonoid (6.71 mg/g-DW) content. Moreover, AgAuNPs (3:1) without NAA enhanced antioxidant activity (87.85 %). This study provides the first evidence of NP effect on callus culture development and production of natural antioxidants in P. vulgaris.

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Mentha species are used in every day life in various food items. These species produce valuable secondary metabolites that scavenge toxic free radicals. Toxic free radicals can cause different diseases in the human body. In the present study free radical scavenging potential (1,1-diphenyl-2-picrylhydrazyl scavenging activity) in nine Mentha species were investigated to evaluate and explore new potential sources for natural antioxidants. The activity was performed after different time intervals with incubation period of 30 minutes. The methanolic extracts revealed that significantly higher activity (82%) was observed in Mentha suaveolens, followed by Mentha longifolia (79%), Mentha officinalis (76%) and Mentha piperita, Mentha pulegium, Mentha royleana (75%), respectively. Significantly same activity was observed in Mentha arvensis and Mentha spicata. Lower activity was observed in Mentha citrata (64%). The present study revealed that these species can be used as natural antioxidants.

The callogenic and shoot organogenic potential of the medicinaly important plant, S. rebaudiana were investigated. Callus induction and shoot regeneration were induced from flower explants of greenhouse plants incubated on Murashige and Skoog (MS)-medium supplemented with different plant growth regulators (PGRs). The best callogenic response was observed on explants incubated on MSmedium supplemented with 2.0 mg/l 6-benzyladenine (BA) along with 2.0 mg/l 2,4-dichlorophenoxyacetic acid (2,4-D) after 30-days of culture. Subsequent transfer of callogenic explants onto MS-medium supplemented with 2.0 mg/l BA gave 85.2% shoot organogenesis after 30-days following culture. Maximum number (21.6) of shoots/explant was recorded for 2.0 mg/l BA. Subsequent sub culturing of shoots after 3 weeks of culture, on medium with similar compositions of PGRs gave 5.1 cm longest shoot. The palynology of S. rebaudiana has also been investigated.

(2019) Sustainable production of biomass and industrially important secondary metabolites in cell cultures of selfheal (Prunellavulgaris L.) elicited by silver and gold nanoparticles,