Biological screening of herbal extracts and essential oil from Plectranthus species: α-amylase and 5-lipoxygenase inhibition and antioxidant and anti-Candida potentials

Abstract The phenolic compound content, the antioxidant and α-amylase inhibition potentials of different extracts of the Plectranthus amboinicus, P. barbatus and P. ornatus were evaluated. We also evaluated the influence of plant growth and harvest time on the chemical composition of the essential oil (EO) of P. amboinicus, its antioxidant and anti-Candida activities and the α-amylase and lipoxygenase inhibitions. The turbo-extract of P. barbatus showed the greatest phenolic compound content and antioxidant activity. No α-amylase inhibition activity was observed in the analyzed extracts, but the turbo-extraction and refluxing extracts possessed high antioxidant activities. Protected cultivation and morning harvest conditions gave the best antioxidant activities, which was associated to the highest carvacrol content. P. amboinicus EO antioxidant activity could contribute to the reduction of oxidative stress in diabetes. Causal Candida strains of diabetic foot ulcers showed sensitivity to P. amboinicus EO. C. albicans and C. dubliniensis were the most sensitive of the selected Candida strains. Turbo-extracts or refluxing of the three species extracts and the EO of P. amboinicus should be considered as a potential candidate for the management the complications of type 2 diabetes.

摘要 本研究评估了香茶菜属（Plectranthus）三个物种——到手香（P. amboinicus）、P. barbatus及P. ornatus——不同提取物的酚类化合物含量、抗氧化活性及α-淀粉酶（α-amylase）抑制潜力。同时探究了植株生长条件与采收时间对到手香精油（essential oil, EO）的化学成分、抗氧化与抗念珠菌活性，以及α-淀粉酶和脂氧合酶抑制活性的影响。P. barbatus的涡轮提取物显示出最高的酚类化合物含量与抗氧化活性。在所分析的提取物中未检测到α-淀粉酶抑制活性，但涡轮提取物与回流提取物均表现出较高的抗氧化活性。保护性栽培与清晨采收条件可获得最佳抗氧化活性，这与最高的香芹酚（carvacrol）含量密切相关。到手香精油的抗氧化活性或可用于缓解糖尿病患者的氧化应激。糖尿病足溃疡的致病性念珠菌菌株对到手香精油表现出敏感性。白色念珠菌（C. albicans）与都柏林念珠菌（C. dubliniensis）为受试念珠菌菌株中敏感性最强的菌种。三种香茶菜属植物的涡轮提取物、回流提取物，以及到手香精油，有望成为缓解2型糖尿病并发症的潜在候选制剂。