2.3.2.2 Prepare the standard working stock solution
2.3.2.2.1 Preparation of standard working stock solution
0.1g of the mixed standard solution of 10 kinds of mixed elements and
0.1g of the nitrogen standard of Se element were respectively accurately
weighed, and diluted to 10 mL with 2% nitric acid to form the mixed
standard stock solution (1000 ng/mL) containing 11 metal elements.
2.3.2.2.2 Preparation of series of standard stocking solution
Appropriate amount of the above standard working stock solution was
weighed accurately, and which was diluted with 2% nitric acid to a
standard series of mixed solutions containing 0.2ng, 1ng, 5ng, 10ng,
50ng, 100ng and 500ng of each element per 1mL.
2.3.2.2.3 Preparation of internal standard working solution
Appropriate amount of the mixed internal standard solution was
accurately weighed and diluted with 2% nitric acid to 50 ng/mL.
2.3 In vitro biological evaluation
2.3.1 In vitro antioxidant effect of the P. nagi kernel
oil
The scavenging ability of P. nagi kernel oil to DPPH⸱ was carried
out in this work. Briefly, 5mg DPPH was added into a 25mL volumetric
flask, and diluted with DMSO to 25mL. The volumetric flask was covered
by a black plastic bag and shaken fully to obtain the DPPH stock
solution. Then, taking out 1.8mL DPPH stock solution and diluting with
8.2mL DMSO to 10mL as the working solution, which was measured the
absorbance as A0 at 519nm. Subsequently, 40µL P.
nagi kernel oil was added into 5mL fresh DPPH stock solution and shaken
to mix well, which was also measured the absorbance as A at 519nm. The
DPPH scavenging ability was calculated at the ratio
[(A0-A) / A0 × 100], each experiment
was repeated for 5 times.
2.3.2 Preliminary in vitro anticancer evaluation
The anticancer activity of this oil was evaluated against gastric
cancer, breast cancer (MCF-7), lung cancer(A549) and Hela cell lines
using the counting kit-8 (CCK-8) method 7. The
evaluation process was described elsewhere with some modifications.
Briefly, the oil was dissolved in DMSO at a concentration of 100mg/mL,
then diluted successively with DMSO for eight different concentrations
(100 mg/mL, 50 mg/mL, 25 mg/mL, 12.5 mg/mL, 6.25 mg/mL, 3.125 mg/mL,
1.5625 mg/mL and 0.78125 mg/mL, respectively) as stock solution for
below experiment.