Seasonal variation in content, chemical composition and antimicrobial and cytotoxic activities of essential oils from four Mentha species.

BACKGROUND: The aim of the present study was to appraise variation in the chemical composition, and antimicrobial and cytotoxic activities of essential oils from the leaves of four Mentha species-M. arvensis, M. piperita, M. longifolia and M. spicata-as affected by harvesting season. Disc diffusion and broth microdilution susceptibility assays were used to evaluate the antimicrobial activity of Mentha essential oils against a panel of microorganisms. The cytotoxicity of essential oils was tested on breast cancer (MCF-7) and prostate cancer (LNCaP) cell lines using the MTT assay. RESULTS: The essential oil contents of M. arvensis, M. piperita, M. longifolia and M. spicata were 17.0, 12.2, 10.8 and 12.0 g kg(-1) from the summer and 9.20, 10.5, 7.00 and 9.50 g kg(-1) from the winter crops, respectively. Gas chromatographic-mass spectrometric analysis revealed that mostly quantitative rather than qualitative variation was observed in the oil composition of each species. The principal chemical constituents determined in M. arvensis, M. piperita, M. longifolia and M. spicata essential oils from both seasons were menthol, menthone, piperitenone oxide and carvone, respectively. The tested essential oils and their major components exhibited notable antimicrobial activity against most of the plant and human pathogens tested. The tested essential oils also exhibited good cytotoxicity potential. CONCLUSION: Of the Mentha essential oils tested, M. arvensis essential oil showed relatively better antimicrobial and cytotoxic activities. A significant variation in the content of most of the chemical components and biological activities of seasonally collected samples was documented.

Presence of blood-pressure lowering and spasmolytic constituents in Buddleja crispa.

This aim of this study was to investigate the crude extract of Buddleja crispa (Bc.Cr) and its active constituent(s) for their antihypertensive and antispasmodic activities. The Bc.Cr caused a dose-dependent (3-10 mg/kg) fall in mean arterial pressure in rats under anesthesia. In rabbit aorta preparations, Bc.Cr (0.03-1 mg/mL) caused inhibition of high K(+) (80 mM) precontractions. The Bc.Cr (0.03-1 mg/mL) also inhibited spontaneous and high K(+) precontractions in rabbit jejunum preparations, suggestive of calcium channel blocking (CCB) activity. CCB activity was further confirmed when pretreatment of the tissues with Bc.Cr (0.03-0.10 mg/mL) caused a rightward shift in Ca(++) concentration response curves, similar to verapamil. Among the pure compounds, BdI-H3 was more potent against the high K(+) than spontaneous contractions and was around eight times more potent than Bc.Cr against the spontaneous contractions while the other two compounds, BdI-2 and BH-3 were inactive. Activity-directed fractionation revealed that the hexane fraction was more potent against K(+) precontractions. These data indicate that Bc.Cr possesses a blood-pressure lowering effect, mediated possibly through CCB, though additional mechanism(s) cannot be ruled out. Among the pure compounds, Bdl-H3 is likely to be the active compound involved in the spasmolytic and possibly BP lowering effect of the parent crude extract.

Cardiovascular and airway relaxant activities of peony root extract.

Paeonia emodi (peony) is a well known plant used medicinally to treat hypertension, palpitations, and asthma. Despite its popularity, there are few reports in the scientific literature examining its use in such conditions. We prepared a 70% ethanolic extract of peony root (Pe.Cr) and applied it to segments of guinea pig atria and trachea and rat aorta suspended separately in tissue baths. Activity against arachidonic acid (AA)-induced platelet aggregation was measured in human platelet-rich plasma. Airway relaxant effect was evaluated against acetylcholine (ACh)-induced airway contraction in mouse lung slices loaded with fluo-4. Pe.Cr (0.3-10 mg/mL) showed an atropine-resistant negative inotropic effect in atria. In rat aorta, an endothelium-independent vasodilatory effect (0.3-10 mg/mL) was seen in phenylephrine- and high-K+-induced contractions. Pe.Cr (0.01-1 mg/mL) also inhibited AA-induced platelet aggregation. In isolated trachea, Pe.Cr (0.3-10 mg/mL) relaxed carbachol- and histamine-induced contractions independently of beta-adrenergic receptors. In mouse lung slices, Pe.Cr (0.3-1 mg/mL) inhibited ACh-induced airway narrowing and oscillations of intracellular Ca2+ in airway smooth muscle cells. The results showed cardiosuppressant, vasodilatory, antiplatelet, and tracheal and airway relaxant activities of peony, providing potential justification for its medicinal use in different hyperactive cardiovascular and respiratory disorders.

Muscarinic, Ca(++) antagonist and specific butyrylcholinesterase inhibitory activity of dried ginger extract might explain its use in dementia.

Ginger rhizome (Zingiber officinale) has been used for centuries to treat dementia in South Asia. This study was undertaken to possibly justify its use. A 70% aqueous/methanolic extract of dried ginger (Zo.Cr) was used. Zo.Cr tested positive for the presence of terpenoids, flavonoids, secondary amines, phenols, alkaloids and saponins. When tested on isolated rat stomach fundus, Zo.Cr showed a spasmogenic effect (0.03-5.00 mg mL(-1)); it relaxed the tissue at concentrations > or =5 mg mL(-1). The stimulant effect was resistant to blockade by hexamethonium and methysergide, but sensitive to atropine, indicating activity via muscarinic receptors. In atropinized (0.1 microM) preparations, Zo.Cr (0.3-3.0 mg mL(-1)) relaxed high K(+) (80 mM)-induced contractions, indicating Ca(++) antagonism in addition to the muscarinic effect. This possible Ca(++) antagonist activity was investigated in Ca(++)-free conditions, with the inhibitory effect of the extract tested against contractions induced by externally administered Ca(++). Zo.Cr (0.1-0.3 mg mL(-1)), similar to verapamil (0.03-0.10 microM), shifted the contractions induced by externally administered Ca(++) to the right, thus suggesting an inhibitory interaction between Zo.Cr and voltage-operated Ca(++) channels. Zo.Cr (0.1-3.0 microg mL(-1)) also potentiated acetylcholine peak responses in stomach fundus, similar to physostigmine, a cholinesterase inhibitor. Zo.Cr, in an in-vitro assay, showed specific inhibition of butyrylcholinesterase (BuChE) rather than acetylcholinesterase enzyme. Different pure compounds of ginger also showed spasmolytic activity in stomach fundus, with 6-gingerol being the most potent. 6-Gingerol also showed a specific anti-BuChE effect. This study shows a unique combination of muscarinic, possible Ca(++) antagonist and BuChE inhibitory activities of dried ginger, indicating its benefit in dementia, including Alzheimer's disease.

Ginger facilitates cholinergic activity possibly due to blockade of muscarinic autoreceptors in rat stomach fundus.

Ginger (Zingiber officinale) is a universally known food plant reputed for its medicinal use in gastrointestinal disorders as a prokinetic and laxative. We recently showed that 70% aqueous-methanolic extract of ginger (Zo.Cr) exhibits prokinetic activity in rats via activation of post-synaptic muscarinic M3 receptor in rat stomach fundus. In view of the physiological significance of pre-synaptic muscarinic M1 and M2 autoreceptors, this study was undertaken to further look into the possible mode of action of the prokinetic effect of ginger through inhibition of pre-synaptic muscarinic receptors. Isolated tissue bath experiments were performed with Sprague-Dawley rat stomach fundus strip preparations immersed in Kreb's solution at 37 degrees C. Carbachol (CCh) maximum responses (1 microM) were obtained in rat stomach fundus. Zo.Cr, given in multiple increasing bolus concentrations (0.01-0.1 mg/ml) 10 min prior to administration of CCh, potentiated the CCh peak responses showing that it is possibly inhibiting the pre-synaptic muscarinic receptors. Like wise, increasing bolus concentrations of pirenzepine (0.03-0.3 microM) and himbacine (0.01-0.03 microM), standard muscarinic M1 and M2 antagonists respectively, also potentiated the CCh responses. These results show that ginger, in addition to having a direct cholinergic agonistic effect on the post-synaptic M3 receptors, also has a possible inhibitory effect on pre-synaptic muscarinic autoreceptors, similar to standard muscarinic antagonists, thus reiterating the gastric stimulant effect of this age-old plant.