Formulation development of anti-rheumatoid gel of Saraca asoca (Roxb. ) De Wilde hydroalcoholic extract containing eucalyptus oil and peppermint oil as penetration enhancer

Abstract In the present research investigation, various concentrations of hydro-alcoholic extract of Saraca asoca (Roxb.) De Wilde (family: Caesalpinaceae) dried bark and carbopol polymer at different temperature ranges were optimized for the preparation of gel formulation. Natural penetration enhancers, v.i.z., eucalyptus oil and peppermint oil were incorporated separately in the extract based gel formulations to study the rate of drug permeation across egg membrane, using franz diffusion cell. In vitro anti-arthritis potential of the formulations was also studied using inhibition of albumin denaturation, antiproteinase activity and membrane stabilization method. As per the results of current study, it is established that S. asoca dried bark hydroalcoholic extract based gel prepared using peppermint oil as penetration enhancer exhibited good permeation rate of 8.48% at the end of 3 h. The percentage inhibition of proteins by antiproteinase method at concentration of 50 µg/ml was 50.01±1.00% which was close to 53.92±0.99% as shown by the standard drug, Diclofenac. Also, the percent protein inhibition determined using membrane stabilization method was found to be 49.70±1.00%, however, it was 63.32±0.94% for the standard drug, Diclofenac. Hence, it is concluded that peppermint oil may act as a good candidate for the preparation of potent anti-rheumatic gel preparations.

PEG-induced osmotic stress in Mentha x piperita L.: Structural features and metabolic responses.

The present study investigated whether osmotic stress induced by the exposure of peppermint (Mentha x piperita L.) to moderate and severe stress for short periods of time changes the plant's physiological parameters, leaf anatomy and ultrastructure and essential oil. Plants were exposed to two levels of polyethyleneglycol (50 g L(-1) and 100 g L(-1) of PEG) in a hydroponic experiment. The plants exposed to 50 g L(-1) maintained metabolic functions similar to those of the control group (0 g L(-1)) without changes in gas exchange or structural characteristics. The increase in antioxidant enzyme activity reduced the presence of free radicals and protected membranes, including chloroplasts and mitochondria. In contrast, the osmotic stress caused by 100 g L(-1) of PEG inhibited leaf gas exchange, reduced the essential oil content and changed the oil composition, including a decrease in menthone and an increase in menthofuran. These plants also showed an increase in peroxidase activity, but this increase was not sufficient to decrease the lipid peroxidation level responsible for damaging the membranes of organelles. Morphological changes were correlated with the evaluated physiological features: plants exposed to 100 g L(-1) of PEG showed areas with collapsed cells, increases in mesophyll thickness and the area of the intercellular space, cuticle shrinkage, morphological changes in plastids, and lysis of mitochondria. In summary, our results revealed that PEG-induced osmotic stress in M. x piperita depends on the intensity level of the osmotic stress applied; severe osmotic stress changed the structural characteristics, caused damage at the cellular level, and reduced the essential oil content and quality.

Anatomical, morphological, and phytochemical effects of inoculation with plant growth- promoting rhizobacteria on peppermint (Mentha piperita).

Plant growth-promoting rhizobacteria (PGPR) generally exert their effects through enhancement of plant nutrient status and/or phytohormone production. The effects of PGPR on aromatic plant species are poorly known. We measured plant growth parameters, chlorophyll content, trichome density, stomatal density, and levels of secondary metabolites in peppermint (Mentha piperita) seedlings inoculated with PGPR strains Bacillus subtilis GB03, Pseudomonas fluorescens WCS417r, P. putida SJ04, or a combination of WCS417r + SJ04. The treated plants, in comparison with controls, showed increases in shoot biomass, root biomass, leaf area, node number, trichome density, and stomatal density, and marked qualitative and quantitative changes in monoterpene content. Improved knowledge of the factors that control or affect biosynthesis of secondary metabolites and monoterpene accumulation will lead to strategies for improved cultivation and productivity of aromatic plants and other agricultural crops without the use of chemical fertilizers or pesticides.