Chemical Composition, Antioxidant, Acetylcholinesterase and β-Lactamase Inhibitory Activities of Essential Oils from Clerodendrum cyrtophyllum Turcz. and Clerodendrum fortunatum L.

Clerodendrum cyrtophyllum Turcz. and Clerodendrum fortunatum L. are traditional medicinal plants used for clearing heat, reducing fire, reducing inflammation and detoxification, and relieving cough and analgesia in China. In the current study, the essential oils (EOs) of C. cyrtophyllum and C. fortunatum were obtained by hydrodistillation. The chemical compositions and the contents of the EOs were measured by GC-MS and GC-FID methods. The antioxidant capacity was measured by 1,1-diphenyl-2-picryl-hydrazyl radical (DPPH), 2'-azinobis(3-ethylbenzthiazoline-6-sulphonate) (ABTS) free radical scavenging capacity and ferric reducing antioxidant power (FRAP). The GC and GC-MS analysis results identified 89 and 63 components in the EOs of C. cyrtophyllum and C. fortunatum, accounting for 94.9% and 96.2%, respectively. 1-octen-3-ol, linalool, and hexahydrofarnesyl acetone were reported as the same primary components. The inhibition rates of the DPPH radical scavenger assay were 43.49% ± 0.95% and 27.23% ± 0.40% at 20 mg/mL, while the ABTS radical scavenging assay showed capacities with the IC50 values 2.31 ± 0.05 mg/mL and 7.43 ± 1.80 mg/mL, respectively. The FRAP values (Trolox equivalent antioxidant concentration) were 55.61 ± 2.56 µmol/g and 23.39 ± 1.58 µmol/g, respectively. The C. cyrtophyllum and C. fortunatum EOs showed anti-acetylcholinesterase activity with the IC50 values 289.10 ± 0.43 µg/mL and 1060.00 ± 0.82 µg/mL, and β-lactamase inhibitory activity with the IC50 values 41.34 ± 0.84 µg/mL and 673.50 ± 1.27 μg/mL, respectively. This study makes a substantial contribution to the chemical and biological knowledge expansion on Clerodendrum species EOs from China.