Memory-improving activity of Melissa officinalis extract in naïve and scopolamine-treated rats

Melissa officinalis L. (Labiatae) traditionally used in treating neurological disorders has also been identified as a memory-enhancing herb. The extract of M. officinalis has a cholinergic property. The role of basal forebrain cholinergic neurons, the neurons that are destroyed in Alzheimer's disease (AD), in learning and memory, is also well known. The aim of this study is to investigate the role of cholinergic system on the memory improving activity of M. officinalis extract. The leaves of M. officinalis were extracted with ethanol 80% using the maceration method. Rats received intra-peritoneal injections of M. officinalis extract in different doses (50-400 mg/kg) alone or in combination with scopolamine (1 mg/kg) before being trained in a Morris water maze (MWM) in a single-day training protocol. After training, the acetylcholinesterase enzyme (AChE) activity was measured in the hippocampus. Administration of M. officinalis extract (200 mg/kg) could significantly enhance learning and memory of naïve rats (p<0.001) and significantly ameliorate scopolamine-induced learning deficit, but the effect of the extract was not dose dependent, and doses above 200 mg/kg could neither enhance memory in naïve rats nor reverse scopolamine-induced memory impairment. Also, inhibition of AChE activity was observed in both naïve and scopolamine-induced memory-impaired rats. These results suggest that M. officinalis can improve memory and that the cholinergic property of the extract may contribute to the memory-improving effects observed in this study. Then M. officinalis extract has potential therapeutic value in alleviating certain memory impairment observed in AD.

Investigation of some biologic activities of Swertia longifolia Boiss

Swertia species are widespread in Eastern and Southern Asian countries and used in traditional medicine as anti-pyretic, analgesic, gastro and liver tonic. Among different species, only Swertia longifolia grows in Iran. In this investigation, antioxidant, cytotoxic and acetylcholinesterase inhibitory activities of S. longifolia have been studied. Aerial parts and roots of the plant were collected, dried and extracted with methanol 80% (total extract). Different extracts of the plant were obtained using hexane, chloroform, ethyl acetate, methanol, methanol:water (1:1) and water, respectively. Cytotoxic activity was determined by MTT assay on MDBK, HepG2, MCF7, HT29 and A549 cell lines. Antioxidant activity was measured by 2,2-diphenyl-1-picryl hydrazyl (DPPH) free radicals and acetylcholinesterase inhibitory (AChEI) effect was evaluated based on Ellman's method in 96-well microplates.The results showed no cytotoxicity of the plant extracts on MDBK, HepG2, MCF7, HT29 and A549 cell lines up to 100 μg/ml. All samples showed radical scavenging activity but methanol extract of aerial parts and ethyl acetate extract of the roots showed the highest effects.Total extract of the roots showed higher AChEI activity than the aerial parts. Among different extracts, chloroform and ethyl acetate extracts of the roots and chloroform and methanol:water extracts of the aerial parts were more potent in AChEI assay. It is concluded that aerial parts and roots of the plant are rich in antioxidant agents with no cytotoxicity on selected cell lines up to 100 μg/ml. Moreover, since antioxidant and AChEI activity of compounds play an important role in the treatment of Alzheimer's disorder, this plant might be a potential candidate for isolation of antioxidant and AChEI compounds which could be used as supportive treatment of Alzheimer's disease.

A validated high performance liquid chromatography method for the analysis of thymol and carvacrol in Thymus vulgaris L. volatile oil

Thymus vulgaris L. (Lamiaceae) is a well-known medicinal plant that contains important compounds such as thymol and carvacrol and it has been used in many pharmaceutical dosage forms. Thymol and carvacrol in essential oils are often quantified by gas chromatography (GC) technique but in this work, a validated and reliable high performance liquid chromatography (HPLC) method has been developed for the analysis of these two components in T. vulgaris essential oil. The essential oil of the plant was analyzed by HPLC and GC techniques. The HPLC system consisted of ACE C₁₈ column and an isocratic acetonitrile:water (50:50) as the mobile phase which was kept at a flow rate of 1 ml/min. The method was validated for selectivity, linearity (r² > 0.997 for both thymol and carvacrol), precision (intra-day 0.8-1.9, 1.7-2.6; and inter-day 3.5-4.5, 3.6-4.7) and recovery (97.7%, 97.6%) for thymol and carvacrol, respectively. The limits of detection (LODs) and limits of quantization (LOQs) were calculated to be 2.8, 0.6 µg/ml and 8.6, 1.8 µg/ml for thymol and carvacrol, respectively. The GC system consisted of flame ionization detector (FID) and CP-SIL 8 column. The concentrations of thymol and carvacrol in essential oil obtained by HPLC (41.2%, 4.3%) and GC (40.7%, 4.2%) were compared by statistical methods and they showed good agreement.

A validated method for analysis of Swerchirin in Swertia longifolia Boiss. by high performance liquid chromatography

Swertia spp. (Gentianaceae) grow widely in the eastern and southern Asian countries and are used as traditional medicine for gastrointestinal disorders. Swerchirin, one of the xanthones in Swertia spp., has many pharmacological properties, such as, antimalarial, antihepatotoxic, and hypoglycemic effects. Because of the pharmacological importance of Swerchirin in this investigation, it was purified from Swertia longifolia Boiss. as one of the main components and quantified by means of a validated high performance liquid chromatography (HPLC) technique. Aerial parts of the plant were extracted with acetone 80%. Phenolic and non-phenolic constituents of the extract were separated from each other during several processes. The phenolic fraction was injected into the semi-preparative HPLC system, which consisted of a C₁₈ column and a gradient methanol: 0.1% formic acid mode. Using this method, we were able to purify six xanthones from the plant, in order to use them as standard materials. The analytical method was validated for Swerchirin as one of the most important components of the plant, with more pharmacological activities according to the validation parameters, such as, selectivity, linearity (r² > 0.9998), precision (≤3.3), and accuracy, which were measured by the determination of recovery (98-107%). The limits of detection and quantization were found to be 2.1 and 6.3 μg/mL, respectively. On account of the speed and accuracy, the UV-HPLC method may be used for quantitative analysis of Swerchirin.