Chemical Composition and Antifungal Activity of Essential Oil from the Roots of Tinomiscium petiolare

Published in Khimiya Prirodnykh Soedinenii, No. 4, July–August, 2022, pp. 641–642.

Tinomiscium petiolare Hook. f. & Thomson is a medicinal species of the genus Tinomiscium (Menispermaceae). This species grows naturally in mixed forests at an altitude of 200 to 600 m in tropical Asian countries, including Vietnam [[1]]. According to previous research papers, the roots of T. petiolare are used to treat joint pain, runny nose, and reduce fever, whereas its leaves and stems are used as a medicine to treat severe cuts as well as to cure tooth decay because of its various medicinal properties [[2]]. The phytochemical research into T. petiolare is still scarce. The stem and root materials from East Java produce small amounts of the alkaloids, whereas the roots of the Philippine materials contain tinophyllone [[2], [4]]. Extracts from the branches of T. petiolare also show antibacterial activity against Staphylococcus aureus [[5]]. The literature search has not revealed any reports of the chemical composition and antifungal activity of the root oils of T. petiolare.

The plant material (roots of T. petiolare) was collected at Pu Luong Nature Reserve (20°28′01.4′′N, 105°10′29.9′′E), Thanh Hoa Province, Vietnam, in May, 2020. The species was identified by Dr. Hoang Van Chinh (Hong Duc University) based on morphological characteristics. A voucher specimen (PL1-2020) has been kept in the Herbarium of Hong Duc University, Vietnam. Plant materials were dried at room temperature (≈ 25°C) before the extraction. Two kilograms of plant samples were chopped and hydrodistilled with a Clevenger-type apparatus for 5 h to produce essential oils under normal pressure, according to the Vietnamese Pharmacopoeia [[6]]. The essential oil was dried with anhydrous sodium sulfate and placed in an amber-colored vial for storage at 4°C until analysis.

Gas chromatographic analysis (GC) was performed on Agilent GC 7890A attached to an FID detector from Agilent Technologies, USA, and fitted with an HP-5MS chromatographic column with a length of 60 m, inner diameter (ID) = 0.25 mm, and film thickness of 0.25 μm. Helium was the carrier gas, with a flow rate of 1.0 mL/min. The inlet temperature was 250°C, and the oven temperature program was 60°C to 240°C at 4°C/min. The split ratio was 100:1, and the injection volume was 1 μL. The interface temperature was 270°C. An Agilent GC 7890A chromatograph was equipped with a capillary of molten silica HP-5MS (60 m × 0.25 mm, film thickness 0.25 μm) and communicated with a mass spectrometer (HP 5973 MSD) used for analyzing GC-MS, under similar conditions to those used for GC-FID analysis. The conditions were similar to those described above, with helium (1 mL/min) as the carrier gas. The MS conditions were as follows: ionization voltage of 70 eV; emission current of 40 mA; acquisition and scan range of 35–450 amu with a sampling rate of 1.0 scan/s. The chemical composition of essential oils was determined based on their retention index (RI) based on a series of n-alkanes, as well as by comparison of their mass spectral fragmentation patterns with those stored on the MS library NIST08, Wiley09, HPCH1607 [[7]]. Relative concentrations (%) of the components were calculated based on GC peak area (FID response) without correction factor. The measurements were carried out in triplicate.

The average yield of the essential oil was 0.05% ± 0.01 (v/w) calculated on a dry weight basis. The oil sample was light yellow and lighter than water. The root oil revealed the presence of 57 compounds, representing 87.38% of the total oil (Table 1). It was dominated by oxygenated monoterpenes (39.56%), sesquiterpene hydrocarbons (26.36%), and monoterpene hydrocarbons (8.94%). The main constituents of the root oil were geranial (16.65%) and neral (9.69%).

Table 1. Constituent Composition of Essential Oil from Roots of Tinomiscium petiolare, %

aElution order on HP-5MS column. bRetention indices (RI) on HP-5MS column.

In addition, significant quantities of γ-terpinene (5.50%), β-bisabolene (5.07%), geraniol (4.82%), geranyl acetate (4.70%), and (Z)-ligustilide (4.45%) were also present in the oil. This is to our knowledge the first report on the chemical composition of T. petiolare root oil.

Antifungal activity assays were performed using the broth microdilution method described previously [[8]], and results were expressed as minimum inhibitory concentration (MIC). Results show that the root oil of T. petiolare inhibited the growth of Aspergillus niger with an MIC value of 200 μg/mL. The antifungal activity of essential oil can be explained by the presence of geranial and neral. These two main compounds have antifungal activity, consistent with previously reported literature [[9]].

The authors would like to thank Hong Duc University (Vietnam) and Far Eastern Federal University (Russia) for their support and facilitation to complete this study.