Chemical composition and uterine smooth muscle relaxant activity of essential oils from 10 kinds of blood-activating and stasis-resolving Chinese medicinal herbs.

Ethnopharmacological Relevance: Dysmenorrhea is one of the most common gynecological problems among menstruating females. Blood-activating and stasis-resolving herbs (BASRHs) have been employed to be the first choice for treating dysmenorrhea in China. Especially, the essential oils of some BASRHs have been confirmed to play important roles in the treatment of dysmenorrhea, but the constituents and uterine smooth muscle relaxant activity of some commonly used BASRH essential oils have not been fully assessed, and whether there are differences in the constituents and anti-dysmenorrhea effect among BASRH essential oils has not been evaluated.
Aim of the Study: This study aims to systematically investigate the chemical constituents of 10 BASRH essential oils and assess their uterine smooth muscle relaxant activity and the preliminary mechanism of the most effective essential oil.
Materials and Methods: The chemical constituents of 10 BASRH essential oils were analyzed by Gas Chromatography-Mass Spectrometer. A rat model of dysmenorrhea in vitro was established to investigate the uterine smooth muscle relaxant activity of 10 kinds of essential oils. Rat isolated uterus strips were given different dose of 10 kinds of essential oils (0.04, 0.08, 0.16 mg/mL). The contractile responses were recorded with Power Lab recording system, and contractile tension, contractile frequency, and contractile activity were evaluated. The preliminary mechanism of the essential oil of the rhizomes of Curcuma phaeocaulis Valeton (CPEO) was assessed using a rat model of dysmenorrhea in vivo and in vitro, and rats were given the CPEO (15, 30, and 60 mg/kg) by gavage. The level of Ca ²⁺ in uterine tissue of rats was determined by methyl thyme phenol blue colorimetric and Bradford methods. The effects of CPEO on extracellular Ca ²⁺ influx and intracellular Ca ²⁺ release were evaluated using the isolated uterus.
Results: The results of Gas Chromatography-Mass Spectrometer analysis showed that more than 81 components (content: 1% max appearance) were identified. The main components of the 10 BASRH essential oils were found to be monoterpenoids, sesquiterpenoids, diterpenoids, aromatics, aliphatics, and phthalides. The study of in vitro smooth muscle relaxant activity demonstrated that all the essential oils except the essential oil of the roots of Cyathula officinalis K.C.Kuan markedly decrease the contractile activity, tension, and frequency (P < 0.05 or P < 0.01). Among these oils, CPEO has the most pronounced effect. Further in vivo studies indicated that CPEO can significantly decrease the level of Ca ²⁺ in uterine tissue when compared with the model group (P < 0.05 or P < 0.01). In vitro studies indicated that CPEO can inhibit the extracellular Ca ²⁺ influx and intracellular Ca ²⁺ release in favor of uterine relaxation.
Conclusions: BASRH essential oils play an important role in inhibiting uterine smooth muscle contractions, and sesquiterpenoids and phthalides in BASRH essential oils are important active compounds for relaxing uterine smooth muscle. CPEO is a favorable candidate for developing anti-dysmenorrhea drugs.
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