4 China Academy of Chinese Medical Sciences
Institute of Chinese Materia Medica, Beijing,100011, China,
* Corresponding author, email: czlu@fjirsm.ac.cn, Tel: +86-592-3576166
Abstract : The Podocarpus Nagi kernel oil was prepared
and its chemical constituents were confirmed accordingly in this work.
The constituents and the contents of the obtained oil were identified
as: total flavonoids (4.2%, calculated according to the rutin),
(9Z ,12Z )-9,12-octadecadienoic acid(38.2%), arachidic
acid(0.11%), cis -11-eicosenoic acid(1.40%),cis -11,14-eicosadienoic acid(8.04%), ꞷ-3(0.2%), ꞷ-6(48.0%),
ꞷ-9(21.0%), vitamin E(2.11mg/100g). The microelements in this oil was
also tested using ICP-MS and the results exhibited that this oil
contains numbers of microelements beneficial for human health: such as
V(0.006μg/g), Cr(0.024μg/g), Mn(40.109μg/g), Fe(2.292μg/g),
Co(0.007μg/g), Zn(4.316μg/g), As(0.009μg/g), Se(0.240μg/g),
Sr(0.453μg/g). Then, the oil was evaluated for its in vitroantioxidant effect against DPPH⸱, which exhibited noteworthy scavenging
ability against DPPH⸱. In addition, the oil was also evaluated for its
preliminary in vitro anticancer activity against four cancer cell
lines: the results showed that it exhibited the highest inhibition
against gastric cancer, breast cancer (MCF-7), lung cancer(A549) and
Hela cell lines with the highest inhibitions of 64.30%±2.80,
52.87%±2.57, 93.21%±2.24 and 88.33%±2.08 at the concentrations of
25mg/mL, 25mg/mL, 50mg/mL and 50mg/mL, and with the
IC50s of 48.47mg/mL, 763.14mg/mL, 11.47mg/mL and
23.77mg/mL respectively. These findings demonstrated that this oil can
be regarded as the functional edible oil by comparing the contents of
edible oils used in the field of food.
Key words : Podocarpus Nagi kernel oil; Preparation;
Chemical constituents; Antioxidant activity; Anticancer activity
Introduction
According to the statistics provided by the National Grain and Oil
Information Center, since 1996, China has imported more edible oils than
the total domestic production, and become the largest importer of edible
oils and oilseeds in the world. The self-sufficiency rate of edible oils
in China is currently less than 40%. In China, the oilseeds mainly rely
on rapeseeds, peanuts, flaxseeds etc., which makes it still difficult to
ensure the safe supply of the oilseeds and edible oils. In 2011, the
consumption of edible oils reached 25.15 million tons, while industrial
and other consumption reached 2.5 million tons, totaling 27.65 million
tons, and the annual consumption per person has reached 20.5 kg in
China. Among the edible oils, the import dependence of high-grade woody
(herbaceous) edible oil has reached 95%, and the external dependence of
ordinary edible oils has also reached 68%. Thus, it is urgent to
explore new approaches and new raw oil materials to develop the edible
oils for long-term development.
Podocarpus Nagi (P. nagi , named Zhubai in Chinese),
belonging to the Podocarpaceae family. This plant contains different
kinds of biological components (such as volatile oil, flavonoids,
steroids, sugar and glycosides, lactones, etc.) and it exhibits a wide
spectrum of biological activities: such as hemostasis, bone setting,
anti-bacterial, anti-tumor, antiviral, antioxidant and detumescence
activities 1-4. The peel and fruit of P. nagiare rich in volatile components and oil, and especially the kernel ofP. nagi has an oil content up to about 30%. P. nagi has
many kinds of active components such as abundant unsaturated fatty
acids, flavonoids, β-vanillin, vitamin E and so on 5.
Therefore, the P. nagi kernel oil should be a high-quality
functional edible oil in theory. And according to the folk records of
the Yao Nationality, P. nagi kernel oil has ever been used as an
edible oil 6. However, up to now, P. nagikernel oil has not been used as an edible oil in the field of food yet.
Considering the lack of edible oils in our native state and large scale
of P. nagi kernel is produced ever year, it is very necessary to
study the chemical constituents and relevant biological activities ofP. nagi kernel oil to develop it to the fields of food and
nutrition. In this work, the preparation process, chemical constituents
and relevant biological activities (antioxidant and anticancer
activities) of P. nagi kernel oil were studied.
2. Experimental
2.1 Material and instruments
The P. nagi kernel were collected in September of 2018 from the
Yangli town of Fujian province and which were air-dried and powdered;
other chemicals used for chemical extractions, chemical constituents
analysis and biological evaluations are analytical reagents and
commercially available.
Instruments. ICP-MS was carried out on the Agilent Technologies
7800(USA); Microwave digestion instrument (Mars 6 Classic, China);
Full-wavelength multifunctional microplate reader (Multiskan GO, USA);
Energy-saving water bath steamer (RQ-ZBL-12, China); Yifeng extruding
machine (6Y1.0, China).
2.2 General process of oil
extraction
The oil was obtained according to the below processes. Briefly, 50kg
powdered P. nagi kernel was placed on a steamer with the
mechanical stirring for 20min. Then, the steamed powder was transferred
to a fixed mold with the high pressure device, and squeezed through
pressure-programmed route from 0MPa to 30MPa for 30min to obtain the
light yellow oil, 10kg, yield:20%.
2.3 Chemical components analysis of the obtained oil
2.3.1 Organic chemical components
analysis
The organic components of the obtained oil were analyzed accordingly.
The total flavonoids were determined in accordance with
the《Implementation Manual of Technical Specifications for Health Food
Inspection and Evaluation》(2003 Edition) P1082 [Determination of
Total Flavonoids (Spectrophotometry)]; the fatty acids were determined
according to the method of GB 5009.168-2016; and vitamin E was
determined according to the method of GB 5009.82-2016.
2.3.2 Trace elements analysis
2.3.2.1 Prepare the testing solution
0.5g oil together with 10 mL of 65% nitric acid was added into the
polytetrafluoroethylene (PTFE) digestion tank and the tank was sealed.
The mixture was digested according to the following working conditions
(see to table 1 ; while the conditions of the ICP-MS instrument
see to table 2 ). After completion of the digestion, the tank
was cooled naturally to room temperature and the digestion solution was
transferred to a 50 mL volumetric flask, and the tank was washed with a
small amount of deionized water
for three times and the washing solutions were also added to the
volumetric flask. The volumetric flask was shaken well after filling to
the constant volume with the deionized water to obtain the testing
solution. The blank solution was prepared according to the above method.
Table 1. Conditions of microwave digestion