Detection and analysis of triterpenic compounds in apple extracts

Figures & data

Figure 1. Variation in the quantitative composition of triterpenic compounds in extracts of apple samples depending on the extractant used.

Figure 2. Variation in the quantitative composition of triterpenic compounds in extracts of apple samples depending on the extraction time. Different letters indicate statistically significant differences in the amounts of triterpenic compounds in extracts of apple samples, according to Tukey, at p > 0.05.

Table 1. Characteristics of the quantitative evaluation of triterpenic compounds.

Compound	Confirmed linearity range (µg/mL)	Calibration curve^a	LOD^b (µg/ml)	LOQ^c (µg/ml)	R^2
Corosolic acid	5–80	y = 4710x	0.17	0.50	0.999975
Betulinic acid	6.25–100	y = 6650x	0.15	0.45	0.999798
Oleanolic acid	6.25–100	y = 6720x-179	0.20	0.60	0.999993
Ursolic acid	0.625–100	y = 6290x+ 27.6	0.17	0.50	0.999999

^ax in the calibration equation indicates the concentration of a compound, and y indicates the peak area.

^bLimit of detection

^cLimit of quantification

Table 2. Precision of the HPLC technique for the quantitative evaluation of triterpenic compounds. Concentrations of reference compounds used in the assessment of precision are provided in the Supplementary material (Table S1).

Compound	Relative standard deviation (%) for the peak area
	Intraday^a			Interday^b
	1^st concentration	2^nd concentration	3^rd concentration
Corosolic acid	0.28	0.6	1.3	1.15
Betulinic acid	0.36	0.43	1.48	1.25
Oleanolic acid	0.48	0.84	1.61	1.77
Ursolic acid	0.57	0.53	0.42	0.99

^aRepeatability; ^bIntermediate precision.

Table 3. Variation in the quantitative composition of triterpenic compounds in apple samples of different cultivars.

Compound	Amount of triterpenic compounds, mg/g DW						CV,%
	‘Aldas’	‘Auksis’	‘Connel Red’	‘Ligol’	‘Lodel’	‘Rajka’
Corosolic acid	0.059 ± 0.014^b	0.075 ± 0.016^b	0.110 ± 0.056^b	0.274 ± 0.076^a	0.096 ± 0.017^b	0.232 ± 0.001^a	63.51
Betulinic acid	0.023 ± 0.001^a	0.022 ± 0.005^a	0.022 ± 0.007^a	0.024 ± 0.002^a	0.032 ± 0.005^a	0.030 ± 0.001^a	17.58
Oleanolic acid	0.373 ± 0.011^ab	0.325 ± 0.019^ab	0.323 ± 0.058^ab	0.357 ± 0.058^ab	0.468 ± 0.112^a	0.315 ± 0.016^b	15.93
Ursolic acid	1.179 ± 0.060^d	1.593 ± 0.154^bc	1.535 ± 0.098^c	1.870 ± 0.094^b	2.577 ± 0.142^a	1.624 ± 0.085^bc	27.23
Total	1.635 ± 0.072^d	2.016 ± 0.099^c	1.989 ± 0.088^c	2.525 ± 0.122^b	3.173 ± 0.136^a	2.201 ± 0.106^c	23.72

Different letters in the same row indicate statistically reliable quantitative differences between the apple samples of the studied cultivars, according to Tukey, at p > 0.05

Figure 3. HPLC chromatogram of the acetone extract of the apple peel sample (cultivar ‘Lodel’, λ = 205 nm). 1 - corosolic acid, 2 - betulinic acid, 3 - oleanolic acid, and 4 - ursolic acid.

Table 4. Variation in the quantitative composition of triterpenic compounds in apple peel samples of different cultivars.

Compound	Amount of triterpenic compounds, mg/g DW						CV,%
	‘Aldas’	‘Auksis’	‘Connel Red’	‘Ligol’	‘Lodel’	‘Rajka’
Corosolic acid	0.220 ± 0.030^a	0.254 ± 0.016^a	0.419 ± 0.016^c	0.832 ± 0.055^a	0.651 ± 0.074^b	0.752 ± 0.014^ab	50.0
Betulinic acid	0.039 ± 0.005^d	0.060 ± 0.005^bc	0.083 ± 0.003^a	0.049 ± 0.013^cd	0.071 ± 0.006^abc	0.081 ± 0.008^ab	27.6
Oleanolic acid	0.989 ± 0.105^b	1.121 ± 0.120^ab	1.240 ± 0.109^a	0.945 ± 0.062^b	1.170 ± 0.101^ab	1.161 ± 0.050^ab	10.3
Ursolic acid	4.023 ± 0.312^c	5.582 ± 0.505^ab	5.798 ± 0.066^ab	4.809 ± 0.797^bc	6.434 ± 0.314^a	5.683 ± 0.279^ab	15.7
Total	5.271 ± 0.220^d	7.016 ± 0.382^bc	7.539 ± 0.419^ab	6.635 ± 0.256^c	8.327 ± 0.391^a	7.677 ± 0.303^ab	14.9

Different letters in the same row indicate statistically reliable quantitative differences between the apple samples of the studied cultivars, according to Tukey, at p > 0.05.

Table 5. Variation in the quantitative composition of triterpenic compounds in apple flesh samples of different cultivars.

Compound	Amount of triterpenic compounds, mg/g DW						CV,%
	‘Aldas’	‘Auksis’	‘Connel Red’	‘Ligol’	‘Lodel’	‘Rajka’
Corosolic acid	0.007 ± 0.003^d	0.007 ± 0.003^d	0.028 ± 0.001^bc	0.035 ± 0.003^b	0.020 ± 0.007^c	0.067 ± 0.003^a	82.0
Betulinic acid	0.012 ± 0.001^a	0.003 ± 0.001^c	ND	0.006 ± 0.001^b	ND	0.008 ± 0.002^b	52.8
Oleanolic acid	0.025 ± 0.008 ^b	0.034 ± 0.002 ^b	0.039 ± 0.016 ^b	0.046 ± 0.014 ^b	0.026 ± 0.004 ^b	0.093 ± 0.013 ^a	58.5
Ursolic acid	0.123 ± 0.035^cd	0.203 ± 0.016^b	0.101 ± 0.005^de	0.069 ± 0.007^e	0.160 ± 0.006^bc	0.249 ± 0.012^a	44.3
Total	0.167 ± 0.006^d	0.247 ± 0.011^b	0.168 ± 0.015^d	0.156 ± 0.007^d	0.205 ± 0.007^c	0.417 ± 0.027^a	43.7

Different letters in the same row indicate statistically reliable quantitative differences between the apple samples of the studied cultivars, according to Tukey, at p > 0.05.