Radical scavenging and antibacterial activity of three Parmotrema species from Western Ghats of Karnataka, India.

Western Ghats are one of the biodiversity hotspots in the world. The present study was conducted to determine antibacterial and radical scavenging potential of three Parmotrema species viz., P. tinctorum, P. grayanum and P. praesorediosum from Maragalale and Guliguli Shankara, Western Ghats of Karnataka, India. The powdered lichen materials were extracted using methanol. Antibacterial activity of lichen extracts was tested against three Gram positive and five Gram negative bacteria by Agar well diffusion assay. Radical scavenging activity of lichen extracts was determined by DPPH free radical scavenging assay. Total phenolic content of lichen extracts was estimated by Folin-Ciocalteau reagent method. The lichen extracts showed dose dependent antibacterial activity. Overall, the lichen extracts were more inhibitory to Gram positive bacteria than Gram negative bacteria. P. grayanum displayed high inhibitory activity against test bacteria. Scavenging of DPPH radicals by lichen extracts was concentration dependent. Among the lichen species, P. grayanum showed higher scavenging potential as indicated by lower IC50 value. Total phenolic content was also high in P. grayanum. Thin layer chromatogram revealed the presence of Lecanoric acid, Orsellinic acid, Protolichesterinic acid, Chloroatranorin, Protopraesorediosic acid and Praesorediosic acid in lichen samples. The observed bioactivities of lichens could be ascribed to the presence of secondary metabolites. These lichens can be considered as suitable candidates for development of bioactive agents active against pathogenic microbes and oxidative damage.

Antimicrobial and antioxidant activities of a macrolichen Usnea pictoides G. Awasthi (Parmeliaceae).

Lichens are self-sufficient symbioses between an alga and a fungus. In the present study, we have determined total phenolic content, antimicrobial and antioxidant efficacy of a macrolichen Usnea pictoides G.Awasthi (Parmeliaceae) collected at Mullayanagiri, Western Ghats of Chikmagalur, Karnataka, India. The lichen was powdered and extracted sequentially using solvents of increasing polarity viz., petroleum ether, chloroform, ethyl acetate and methanol. Total phenolic content of solvent extracts was estimated by Folin-Ciocalteau reagent method. Antimicrobial activity of solvent extracts was tested against two bacteria viz., Staphylococcus aureus and Pseudomonas aerugionsa and two fungi viz., Candida albicans and Cryptococcus neoformans by Agar well diffusion assay. Antioxidant activity of solvent extracts was determined by DPPH free radical scavenging assay and Ferric reducing assay. Thin layer chromatogram showed the presence of usnic acid. The total phenolic content was highest in methanol extract followed by ethyl acetate, chloroform and petroleum ether extracts. S. aureus and C. neoformans showed high susceptibility to solvent extracts among bacteria and fungi. A dose dependent scavenging of DPPH radicals by solvent extracts was observed. The scavenging potential of methanol extract was higher than other extracts. In ferric reducing assay, methanol extract showed stronger reducing power than other extracts. Overall, extracts containing high phenolic contents exhibited stronger antioxidant activity. The inhibitory potential of the lichen extracts might be attributed to the presence of usnic acid. The radical scavenging and ferric reducing potential of solvent extracts could be attributed to the phenolic compounds. A positive correlation was observed between total phenolic content and the antioxidant activity of lichen extracts. The lichen U. pictoides can be a potential candidate for the development of bioactive agents.

Antioxidant and antimicrobial activity of flowers of Wendlandia thyrsoidea, Olea dioica, Lagerstroemia speciosa and Bombax malabaricum.

Flowers of higher plants have been used for centuries for several purposes such as medicine, food and garnishing food in many parts of the world. In the present study, we have determined the antioxidant and antimicrobial activity of methanol extract of flowers of Wendlandia thyrsoidea (Roemer & Schultes) Steudel (Rubiaceae), Olea dioica Roxb. (Oleaceae), Lagerstroemia speciosa L. (Lythraceae) and Bombax malabaricum DC. (Bombacaceae). Antioxidant efficacy of various concentrations of flower extracts was evaluated by DPPH free radical scavenging assay and Ferric reducing assay. Antimicrobial activity was determined against four bacteria and two fungi by agar well diffusion method. Total phenolic and flavonoid contents were determined by Folin-Ciocalteau reagent and Aluminium chloride colorimetric estimation methods respectively. The DPPH free radical scavenging effect of flower extracts was concentration dependent and was higher in case of extract of L. speciosa followed by W. thyrsoidea, B. malabaricum and O. dioica. In ferric reducing assay, it was shown that the absorbance of reaction mixture at 700nm increased on increasing the concentrations of flower extracts indicating reducing power of extracts. The reducing ability was also highest in L. speciosa extract. Extract of L. speciosa displayed marked inhibitory activity against bacteria and fungi than other flower extracts. Gram positive bacteria have shown more susceptibility than Gram negative bacteria. Among fungi, C. neoformans was more inhibited than C. albicans. Extracts of B. malabaricum and O. dioica were not effective against C. albicans. The phenolic and flavonoid contents were higher in L. speciosa and O. dioica respectively. A positive correlation has been observed between total phenolic content of flower extracts and antioxidant and antimicrobial activity. The flowers can be employed as a remedy for treatment of infectious diseases and oxidative damage. Further, isolation of active components from flower extracts and their biological activity determinations are under progress.

Anticariogenic Activity of Gnidia glauca (Fresen.) Gilg, Pothos scandens L. and Elaegnus kologa Schlecht.

The present study was conducted to estimate total phenolic and flavonoid content and to determine anticariogenic efficacy of methanol extract of Gnidia glauca (Fresen.) Gilg (Thymelaeaceae), Pothos scandens L. (Araceae) and Elaegnus kologa Schlecht (Elaeagnaceae) leaves. Total phenolic and flavonoid content of leaf extracts was determined by Folin-Ciocalteau method and Aluminium chloride colorimetric estimation method respectively. Anticariogenic activity of leaf extracts was assessed against 13 clinical isolates of Streptococcus mutans by Agar well diffusion technique. The contents of total phenolics and flavonoids were higher in G. glauca followed by P. scandens and E. kologa. The extract of G. glauca showed greater inhibition of cariogenic isolates than P. scandens and E. kologa as revealed by wider inhibition zones. The study revealed a correlation between the amount of phenolics and flavonoids present in the extracts and the anticariogenic activity of the extracts. The plants used in this study could be used against dental caries.