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）是一种流传数百年的知名传统药材，兼具确切治疗功效。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）对人阴茎海绵体（human corpus cavernosum, HCC）及大鼠阴茎海绵体（rat corpus cavernosum, CC）的作用。首先对肉桂精油的成分谱进行了分析验证。
本研究纳入因行阴茎假体植入术获取的HCC标本（患者年龄48~69岁）用于功能学实验；此外，通过体内实验评估了麻醉状态下正常对照及糖尿病大鼠在海绵体内注射CEO与CA后的勃起反应，并将大鼠阴茎海绵体条置于器官浴槽中开展离体检测。
在使用10μM去氧肾上腺素（phenylephrine）预收缩标本后，本研究考察了CEO与CA的舒张反应。成分分析结果显示，肉桂醛（CA）为肉桂精油的主要成分，占比达96.9%。CEO与CA对HCC的最大舒张反应分别为96.4±3.5%与96.0±5.0%，对大鼠阴茎海绵体的最大舒张反应则分别为97.5±5.5%与96.8±4.8%。
正常对照大鼠与糖尿病大鼠对CEO与CA的舒张反应无显著差异。在阴茎海绵体组织中，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）存在时，精油与CA诱导的舒张反应未受到明显减弱。
体内实验结果显示，糖尿病大鼠的勃起反应低于正常对照大鼠，而经海绵体内注射CEO与CA后，该勃起功能缺陷得以恢复。
综上，CEO与CA可通过不依赖一氧化氮/环磷酸鸟苷（NO/cGMP）的通路改善大鼠阴茎海绵体及人阴茎海绵体条的舒张功能，进而提升勃起功能。未来需开展进一步研究，以全面阐明CEO与CA对糖尿病性勃起功能障碍的修复作用机制。