Roles Conceptualization, Data curation, Formal analysis, Funding acquisition, Investigation, Methodology, Project administration, Resources, Software, Supervision, Validation, Visualization, Writing – original draft, Writing – review & editing * E-mail: wyhhngydx2014@163.com Affiliation School of Food Science and Technology, Henan University of Technology, Zhengzhou, China
Roles Data curation, Investigation, Methodology, Writing – review & editing Affiliation School of Food Science and Technology, Henan University of Technology, Zhengzhou, China ⨯
Xanthoxylin was the main compound (content 44.92% of total volatiles) in the leaves of Luodian B. balsamifera, which might be the key cause of failure in collecting essential oil (EO) of the leaves using general hydrodistillation in Clevenger apparatus. A modified hydrodistillation equipped with Clevenger apparatus was designed for isolating EO from the leaves. Six EOs of Luodian B. balsamifera harvested once a month from September to next February were collected successfully. The main components of EOs were δ-elemene, α-cubenene, caryophyllene, caryophyllene epoxide, γ-eudesmol, xanthoxylin, and α-eudesmol. The EOs of Luodian B. balsamifera collected from October to December had higher antioxidant activities (ACs). Combining the principal component analysis of chemical components with the results of ACs and the yields of six EOs, the leaves of Luodian B. balsamifera were suitable to be harvested in November and December to obtain EO with high quality.
Citation: Wang Y-H, Zhang Y-R (2020) Variations in compositions and antioxidant activities of essential oils from leaves of Luodian Blumea balsamifera from different harvest times in China. PLoS ONE 15(6): e0234661. https://doi.org/10.1371/journal.pone.0234661
Editor: Ram Roshan Sharma, ICAR- Indian Agricultural research Institute, INDIA
Received: January 10, 2020; Accepted: May 30, 2020; Published: June 16, 2020
Copyright: © 2020 Wang, Zhang. This is an open access article distributed under the terms of the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original author and source are credited.
Data Availability: All relevant data are within the manuscript and its Supporting Information files.
Funding: The leaves of Luodian Blumea balsamifera were collected from planting base belonging to Gui Zhou Ai Yuan Eco-Pharmaceutical Development Co. Ltd. (abbreviation: Ai Yuan). Ai Yuan received the support of the local government and the support of Chinese Innovation Fund for Technology Based Firms and Guizhou’s Innovation Fund for Technology Based Firms. The authors have a confidential cooperative relationship with Ai Yuan. This work was supported by Henan University of Technology under Henan University of Technology High-level Talents Fund (2015BS009). The funders had no role in study design, data collection and analysis, decision to publish, or preparation of the manuscript.
Competing interests: The authors collected leaves of Luodian Blumea balsamifera from the Ai Yuan planting base. Ai Yuan received the support of the local government and the support of Chinese Innovation Fund for Technology Based Firms and Guizhou’s Innovation Fund for Technology Based Firms. The authors have a confidential cooperative relationship with Ai Yuan. This does not alter our adherence to PLOS ONE policies on sharing data and materials. There are no patents, products in development or marketed products to declare.
Blumea balsamifera (L.) DC. (Asteraceae) is an aromatic plant and a traditional herb cultivated in East Asia and Southeast Asia [1,2]. The leaves of B. balsamifera are rich in volatile compounds and can be used to collect essential oil (EO), and EO is found to possess antimicrobial and insecticidal activities [3–6]. Besides, the crude extracts, flavonoids, sesquiterpenoids, and triterpenoids were extracted from the leaves of B. balsamifera [7–12]. B. balsamifera, also named Ainaxiang, harvested from Yunnan and Hainan Province, China, had been used to extracted EOs using hydrodistillation according to the method noted in Pharmacopoeia of the People’s Republic of China, and the compositions and antioxidant activities of EOs of different plant organs from B. balsamifera at different growth times were analysed and evaluated [13]. As is well known, the same species of plants cultivated in different regions have great differences in chemical composition [14]. B. balsamifera is a genuine Miao nationality herb which is cultivated in Luodian County, China, and is locally called as “Qian Ainaxiang” [15], and Luodian B. balsamifera is an important source of l-borneol [16]. The volatile oil of Luodian B. balsamifera had been extracted by hydrodistillation and organic solvent extraction in previous researches [17,18]. However, no information about the EO of Luodian B. balsamifera collected using Clevenger apparatus has appeared on the relevant investigation.
The preparation method of EO has been strictly defined, and the accurate specification is recorded in European Pharmacopoeia [19]. Clevenger apparatus is the classical laboratory equipment based on the circulatory distillation approach for collecting EO [20]. It must be noted that the entire distillate (hydrolate and oil) is not extracted with a solvent. Otherwise, the crude product cannot be called any longer an EO, it is just a solvent extract from the distillate [21]. The previous literatures recorded that organic solvent was used in the distillation process of Luodian B. balsamifera for collecting the extracts [15,17], therefore, the product was called a solvent extract rather than EO, including the remains recovered using some solvent from the walls of the glassware (Clevenger apparatus). The solvent-free extraction of EO is a green preparation process and is worth to be investigated. In our previous work, the EO of Luodian B. balsamifera leaves was collected unsuccessfully by the ordinary hydrodistillation in Clevenger apparatus. However, l-borneol was present on the inner wall of the condenser in the hydrodistillation, and the purity of l-borneol was 82% [22]. The above results can be used as a reference, and a modified hydrodistillation method was designed using volatile oil extraction apparatus (VOEA) recorded in the Chinese Pharmacopeia to collect EO of Luodian B. balsamifera leaves [23].
In the study, we investigated the reason why we cannot obtain the EO by the general hydrodistillation using Clevenger apparatus more deeply. Moreover, the EOs of Luodian B. balsamifera leaves harvested from different times were collected using Clevenger apparatus by the modified hydrodistillation method. The chemical components of EOs were determined by GC-FID and GC-MS, the antioxidant activities of EOs were evaluated by DPPH radical scavenging test, β-carotene bleaching (BCB) test, and thiobarbituric acid reactive species (TBARS) assay. Moreover, the optimum harvest time of Luodian B. balsamifera leaves was reported.
The leaves were randomly collected from B. balsamifera cultivated in planting base (the planting base belongs to Gui Zhou Ai Yuan Eco-Pharmaceutical Development Co. Ltd) in Luodian County (Southwest China, 25° 04′ N; 106° 28′ E), and the samples were collected once a month from September 2016 to February 2017. The plant was identified by Prof. Y.N. He (Institute of Biotechnology, Guizhou Academy of Agricultural Sciences, China), and a voucher specimen (CGA-Dafengai-Guizhou-2009-11) was deposited in the Institute of Biotechnology, Guizhou Academy of Agricultural Sciences. The leaves were air-dried in the room and then were milled into 80 mesh powder before hydrodistillation.
n-Hexane (99%), l-borneol (97%), xanthoxylin (97%) and 1,1-diphenyl-2-picrylhydrazyl (DPPH, 95%) were purchased from Sigma-Aldrich (Shanghai, China). β-carotene was purchased from Fluka Chemie (Buchs, Switzerland). Thiobarbituric acid, anhydrous Na2SO4, and all of the applied solvents (analysis purity) were purchased from Sinopharm Chemical Reagent Co. Ltd. (Shanghai, China). For Linear retention indices (RIs) determination, a hydrocarbon mixture (C8–C30 n-alkanes) purchased from Supelco (Ballefonte, USA) was used to perform in the same condition as real sample determination.
For the measurement of response factors, the chemicals used were: l-borneol, ledol, γ-eudesmol, β-eudesmol, 1-octen-3-ol, linalool, nerolidol, 3-octanol and α-terpineol for alcohols; pentadecanal for aldehydes; camphor, zierone and xanthoxylin for ketones; hexadecanoic acid for acids; β-pinene for monoterpene hydrocarbons; α-muurolene, δ-cadinene caryophyllene and α-caryophyllene for sesquiterpene hydrocarbons; caryophyllene epoxide for oxides; 1,2-dihydro-1,1,6-trimethyl-naphthalene for aromatic hydrocarbons.
Fifty grams dried leaves of B. balsamifera were distilled to collect 5 L of distillate (distillation time: 10 h), and the distillate was collected for extracting total volatiles (TV) of the leaves using same volume anhydrous diethyl ether under room temperature. The extract solution was dehydrated with anhydrous sodium sulfate and concentrated to obtain total volatiles. The TV was stored at –20°C in dark glass bottles until required. The process was executed in ten replicates.
The general hydrodistillation was executed in Clevenger apparatus. Fifty grams of leaves samples and 1 L distilled water were added into 2 L flask and distilled for 10 h in Clevenger apparatus (Jingbo, Jintan, China) (Fig 1A). In the end, there was no EO to be collected. However, there were white volatile on the surface of condenser inner wall and an aqueous phase (aromatic water) in Clevenger apparatus. The aqueous phase was extracted by diethyl ether anhydrous (100 mL), and the extraction solution was concentrated under vacuum. White volatiles (WV) and the extract of aqueous phase (EAP) were weighed and stored at 4°C in dark glass bottles until analysis, respectively. The experiments were executed with six replicates.