Evaluation of relaxant responses properties of cinnamon essential oil and its major component, cinnamaldehyde on human and rat corpus cavernosum

ABSTRACT Cinnamomum cassia (Cinnamon) is a well-known traditional medicine with therapeutic benefits for centuries. We evaluated the effects of cinnamon essential oil (CEO) and its main component cinnamaldehyde (CA) on human corpus cavernosum (HCC) and rat CC. The essential oil of cinnamon was analyzed for the confirmation of the oil profile. HCC specimens from patients undergoing penile prosthesis surgery (age 48-69 years) were utilized for functional studies. In addition, erectile responses in anesthetized control and diabetic rats were evaluated in vivo after intracavernosal injection of CEO and CA, and rat CC strips were placed in organ baths. After precontraction with phenylephrine (10µM), relaxant responses to CEO and CA were investigated. CA (96.9%) was found as the major component. The maximum relaxation responses to CEO and CA were 96.4±3.5% and 96.0±5.0% in HCC and 97.5±5.5% and 96.8±4.8% in rat CC, respectively. There was no difference between control and diabetic rats in relaxation responses to CEO and CA. The relaxant responses obtained with essential oil and CA were not attenuated in the presence of nitric oxide synthase (NOS) inhibitor, and soluble guanylate cyclase inhibitor (sGS) in CC. In vivo, erectile responses in diabetic rats were lower than in control rats, which was restored after intracavernosal injection of CEO and CA. CEO and CA improved erectile function and relaxation of isolated strips of rat CC and HCC by a NO/cGMP-independent mechanism. Further investigations are warranted to fully elucidate the restorative effects of CEO and CA on diabetic erectile dysfunction.

摘要 肉桂（Cinnamomum cassia）是一种享誉数百年的经典传统药物，兼具多种治疗功效。本研究评估了肉桂精油（cinnamon essential oil, CEO）及其主要成分肉桂醛（cinnamaldehyde, CA）对人海绵体组织（human corpus cavernosum, HCC）及大鼠海绵体的作用。首先对肉桂精油开展成分分析以确认其组分特征。本研究采用接受阴茎假体植入术的患者（年龄48~69岁）的HCC标本开展功能学研究。此外，本研究通过体内实验评估了麻醉状态下对照大鼠与糖尿病大鼠在海绵体内注射CEO及CA后的勃起反应，并将大鼠海绵体肌条置于器官浴槽中进行检测。在使用苯肾上腺素（phenylephrine, 10µM）预收缩肌条后，本研究考察了肌条对CEO与CA的舒张反应。结果显示，CA为肉桂精油的主要成分，占比达96.9%。在HCC标本中，CEO与CA的最大舒张率分别为96.4±3.5%与96.0±5.0%；在大鼠海绵体组织中则分别为97.5±5.5%与96.8±4.8%。对照大鼠与糖尿病大鼠对CEO及CA的舒张反应无显著差异。当使用一氧化氮合酶（nitric oxide synthase, NOS）抑制剂与可溶性鸟苷酸环化酶抑制剂（soluble guanylate cyclase inhibitor, sGS）时，精油与CA介导的舒张反应未出现衰减。体内实验结果表明，糖尿病大鼠的勃起反应低于对照大鼠，但经海绵体内注射CEO与CA后，该缺陷可得到恢复。CEO与CA可通过不依赖一氧化氮/环磷酸鸟苷（NO/cGMP）的通路改善勃起功能，同时舒张大鼠海绵体肌条与分离的人海绵体组织。后续仍需开展进一步研究，以充分阐明CEO与CA对糖尿病性勃起功能障碍的修复作用机制。