Desirability Function Approach for the Optimization of Hydroalcoholic Solvent Extraction Conditions for Antioxidant Compounds from Olive Leaves

VURAL, NİLÜFER; ALGAN-CAVULDAK, ÖZGE; AKAY, M. ABDÜLKADİR

doi:10.1590/0001-3765202420230602

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CHEMICAL SCIENCES • An. Acad. Bras. Ciênc. 96 (1) • 2024 • https://doi.org/10.1590/0001-3765202420230602 copy

Desirability Function Approach for the Optimization of Hydroalcoholic Solvent Extraction Conditions for Antioxidant Compounds from Olive Leaves

Authorship SCIMAGO INSTITUTIONS RANKINGS

Abstract

The goal of this work was to obtain a rich olive leaf extract with high antioxidant activity due to its content of oleuropein (OLE), hydroxytyrosol (HT) and other phenolics, which have a synergistic effect on total antioxidant activity (TAA). The extraction parameters in the solvent extraction were investigated using response surface methodology (RSM) to produce the best results of HT and TAA in olive leaf extracts. A Box Wilson-CCD design was applied, the multi-objective optimization (MOO) was computed with Pareto solutions, and the desirability function (DF) was employed to define the best process variables. The optimized conditions (solvent concentration, temperature, time, solvent:solid ratio) were as follows: 63.30 %, 36 °C, 62 min, 11.80 mL/g for MeOH:H20 extracts and 43.80 %, 52 °C, 58 min, 9.40 mL/g for EtOH:H2 O extracts. Under these conditions, the highest results of HT were reached to 0.809±0.110 mg/g dw and 0.175±0.004 mg/g dw for MeOH:H2 O and EtOH:H2 O extracts, respectively. Similarly, the best results for TAA were obtained at higher concentrations in MeOH:H2 O extracts (451±2.32 mM Trolox) than in EtOH:H2O extracts (297±0.817 mM Trolox). Overall, the synergistic effect of OLE, HT, and flavonoids could make the olive leaf extract a potential cheap source for high value-added products.

Key words
Total antioxidant activity (TAA); Hydroxytyrosol (HT); Desirability function; optimization; method validation

Coded levels						Coded levels
Independent variables	-α	-1	0	+1	+α	Independent variables	- α	-1	0	+1	+α
X₁: MeOH conc (% v/v)	12	25	45	65	79	X’₁: EtOH conc (% v/v)	12	25	45	65	79
X₂: Temperature (°C)	20	30	45	60	70	X’₂: Temperature (°C)	20	30	45	60	70
X₃: Time (min)	8	25	50	75	92	X’₃: Time (min)	8	25	50	75	92
X₄:Solvent:solid ratio (mL/g)	2	5	9.5	14	17	X’₄: Solvent:solid ratio (mL/g)	2	5	9.5	14	17

	Std	x1	x2	x3	x4	Y ₁	Y ₂	Ty (mg/g dw)	L7G (mg/g dw)	OLE (mg/g dw)	A7G (mg/g dw)	Lut (mg/g dw)
		MeOH conc (%v/v)	Temp. ( °C)	Time (min)	Solvent: solid ratio (mL/g leaf)	HT (mg/g dw)	TAA (mM Trolox)	Ty (mg/g dw)	L7G (mg/g dw)	OLE (mg/g dw)	A7G (mg/g dw)	Lut (mg/g dw)
	1	65(+1)	60(+1)	75(+1)	5(-1)	0.083±0.001	472±1.99	0.81±0.080	0.005±0.001	12.56±0.31	0.21±0.025	0.08±0.009
	2	65(+1)	60(+1)	25(-1)	5(-1)	0.983±0.121	485±1.89	0.39±0.002	0.016±0.002	6.54±0.22	0.18±0.017	0.08±0.010
	3	65(+1)	30(-1)	75(+1)	14(+1)	1.069±0.125	490±1.75	0.12±0.010	0.024±0.005	4.08±0.18	0.05±0.006	0.04±0.003
	4	25(-1)	60(+1)	25(-1)	14(+1)	0.04±0.001	284±0.85	0.06±0.002	0.012±0.007	1.94±0.08	0.04±0.007	0.01±0.000
	5	65(+1)	30(-1)	25(-1)	14(+1)	0.098±0.002	411±1.01	0.05±0.002	0.012±0.008	3.96±0.11	0.04±0.005	0.01±0.000
	6	25(-1)	30(-1)	75(+1)	5(-1)	0.049±0.001	385±0.98	0.32±0.018	0.031±0.007	6.11±0.18	0.25±0.022	0.04±0.002
	7	25(-1)	60(+1)	75(+1)	14(+1)	0.09±0.002	345±0.87	0.10±0.011	0.001±0.000	2.33±0.09	0.10±0.011	0.04±0.002
	8	25(-1)	30(-1)	25(-1)	5(-1)	0.035±0.001	321±0.76	1.48±0.115	0.093±0.008	4.49±0.16	0.13±0.012	0.01±0.001
	9	12(-1.68)	45(0)	50(0)	9.50 (0)	0.001±0.001	210±0.65	0.14±0.011	0.015±0.002	1.22±0.05	0.04±0.006	0 (nd)
	10	79(1.68)	45(0)	50(0)	9.50 (0)	1.145±0.121	498±0.98	0.21±0.012	0.006±0.001	5.55±0.12	0.08±0.007	0.03±0.002
	11	45(0)	20(-1.67)	50(0)	9.50 (0)	0.11±0.003	397±0.75	0.06±0.003	0.015±0.002	2.15±0.08	0.05±0.004	0 (nd)
	12	45(0)	70(+1.67)	50(0)	9.50 (0)	0.29±0.0025	405±0.98	0.24±0.012	0.003±0.000	4.16±0.14	0.11±0.012	0.06±0.008
	13	45(0)	45(0)	8(-1.68)	9.50 (0)	0.005±0.001	195±0.57	0.001±0.00	0 (nd)	1.02±0.08	0.004±0.000	0 (nd)
	14	45(0)	45(0)	92(+1.68)	9.50 (0)	0.297±0.020	398±0.75	0.15±0.012	0.01±0.003	5.47±0.21	0.16±0.014	0.07±0.005
	15	45(0)	45(0)	50(0)	2(-1.67)	0.074±0.003	359±0.77	0.11±0.008	0.004±0.000	3.51±0.18	0.08±0.005	0.02±0.001
	16	45(0)	45(0)	50(0)	17.00(+1.67)	0.223±0.019	309±0.71	0.05±0.001	0.005±0.000	2.35±0.11	0.07±0.006	0.01±0.000
	17-22	45(0)	45(0)	50(0)	9.50 (0)	0.175±0.012	345±0.74	0.16±0.02	0.013±0.010	3.31±0.14	0.11±0.021	0.04±0.010
Desirability	Opt(Obs)	63.30	36.00	62.00	11.80	0.809±0.110	451±2.32	0.09±0.003	0.018±0.006	9.25±0.23	0.11±0.017	0.05±0.009
Desirability	Opt(Pred)	63.30	36.00	62.00	11.80	0.721	442
	Std	x’1	x’2	x’3	x’4	Y’ ₁	Y’ ₂	Ty (mg/g dw)	L7G (mg/g dw)	OLE (mg/g dw)	A7G (mg/g dw)	Lut (mg/g dw)
		EtOH conc (%v/v)	Temp.( °C)	Time (min)	Solvent:solid ratio (mL/g leaf)	HT (mg/g dw)	TAA (mM Trolox)	Ty (mg/g dw)	L7G (mg/g dw)	OLE (mg/g dw)	A7G (mg/g dw)	Lut (mg/g dw)
	1	65(+1)	60(+1)	75(+1)	5(-1)	0.01±0.000	293±1.11	1.42±0.02	0.68±0.05	7.90±0.11	0.35±0.02	0.11±0.030
	2	65(+1)	60(+1)	25(-1)	5(-1)	0.02±0.001	281±0.98	1.00±0.01	0.21±0.02	4.54±0.07	0.18±0.01	0.091±0.010
	3	65(+1)	30(-1)	75(+1)	14(+1)	0.098±0.009	272±0.77	2.89±0.06	0.419±0.04	2.64±0.03	0.047±0.00	0.032±0.002
	4	25(-1)	60(+1)	25(-1)	14(+1)	0.01±0.001	129±0.23	0.07±0.01	0.11±0.01	0.90±0.01	0.05±0.00	0.01±0.001
	5	65(+1)	30(-1)	25(-1)	14(+1)	0.07±0.002	222±0.39	1.996±0.03	0.321±0.02	1.30±0.02	0.029±0.00	0.02±0.002
	6	25(-1)	30(-1)	75(+1)	5(-1)	0.03±0.000	121±0.21	0.15±0.02	0.137±0.01	0.70±0.01	0.073±0.01	0.03±0.004
	7	25(-1)	60(+1)	75(+1)	14(+1)	0.19±0.010	178±0.18	0.02±0.00	0.199±0.02	2.60±0.03	0.088±0.01	0.023±0.003
	8	25(-1)	30(-1)	25(-1)	5(-1)	0.06±0.002	156±0.17	0.057±0.01	0.115±0.01	0.98±0.01	0.11±0.01	0.028±0.003
	9	12(-1.68)	45(0)	50(0)	9.50 (0)	0.05±0.003	130±0.11	0.001±0.00	0.005±0.00	1.18±0.02	0.07±0.00	0.006±0.00
	10	79(1.68)	45(0)	50(0)	9.50 (0)	0.021±0.001	292±0.41	1.01±0.04	0.385±0.02	3.92±0.05	0.067±0.00	0.04±0.001
	11	45(0)	20(-1.68)	50(0)	9.50 (0)	0.05±0.002	180±0.12	1.00±0.03	0.311±0.03	1.75±0.02	0.05±0.00	0.011±0.00
	12	45(0)	70(+1.68)	50(0)	9.50 (0)	0.25±0.020	298±0.38	1.24±0.04	0.452±0.05	3.79±0.06	0.12±0.01	0.06±0.002
	13	45(0)	45(0)	8(-1.68)	9.50 (0)	0.001±0.000	198±0.13	1.01±0.02	0.332±0.04	0.80±0.01	0.003±0.00	0.002±0.00
	14	45(0)	45(0)	92(+1.68)	9.50 (0)	0.05±0.002	235±0.14	1.11±0.02	0.348±0.04	5.20±0.08	0.09±0.01	0.049±0.001
	15	45(0)	45(0)	50(0)	2(-1.68)	0.14±0.015	288±0.13	0.66±0.01	0.033±0.004	3.40±0.05	0.06±0.01	0.025±0.002
	16	45(0)	45(0)	50(0)	17.00(+1.68)	0.04±0.002	225±0.12	1.01±0.05	0.335±0.05	1.90±0.02	0.044±0.00	0.019±0.001
	17-22	45(0)	45(0)	50(0)	9.50 (0)	0.14±0.01	285±1.05	1.25±0.05	0.442±0.08	3.10±0.05	0.10±0.01	0.041±0.005
Desirability	Opt(Obs)	43.80	52.00	58.00	9.40	0.175±0.004	297±0.817	1.28±0.04	0.475±0.06	4.89±0.07	0.11±0.01	0.07±0.006
Desirability	Opt(Pred)	43.80	52.00	58.00	9.40	0.172	298

Parameter	HT	Ty	L7G	OLE	A7G	Lut
Accuracy^a (mean recovery % ±SD)	97.32±0.51	98.85±1.02	97.98±0.88	95.85±1.45	98.33±0.79	98.43±0.92
Precision
Repeatability^b	±1.01	±0.70	±0.55	±1.70	±0.70	±0.35
Intermediate precision^c	±2.00	±2.25	±1.99	±4.25	±2.25	±1.80
Linearity
Slope	191262	258476	3.10⁷	65974	295601	634194
Intercept	+123121	+114873	-87408	+1.10⁶	196496	300382
Correlation cofficient (r)	0.9979	0.9968	0.9993	0.9952	0.9983	0.9921
Range (mg L−¹)	0.5-100	0.01-20	0.01-20	2.5-1750	0.25-50	0.010-20
LOD^d (mg L−¹)	0.012	0.005	0.008	0.4.10^-3	0.011	0.6.10^-3
LOQ^d (mg L−¹)	0.042	0.015	0.026	1.7.10^-3	0.037	2.0.10^-3

	Y₁:HT				Y₂: TAA
	Hierarchial Terms added after Backward Elimination Regression: X ₄ , X ₁ ² , X ₂ ² , X ₃ ² , X ₅ ² , X ₃ X ₅ , X ₂ X ₄ , X ₄ X ₅ , X ₁ X ₃ , X ₃ X ₄ , X ₂ X ₅ , X ₁ X ₄				Hierarchial Terms added after Backward Elimination Regression: X ₄ , X ₁ ² , X ₂ ² , X ₃ ² , X ₅ ² , X ₃ X ₅ , X ₂ X ₃ , X ₁ X ₃ , X ₂ X ₄ ,X ₁ X ₄ ,X ₄ X ₅ ,X ₃ X ₄ ,X ₂ X ₅
	SSE	df	F value	p value	SSE	df	F value	p value
Model	2.41	9	107.22	< 0.0001	1.099 10⁵	4	16.26	< 0.0001
X₁ (MeOH con.)	0.65	1	262.11	< 0.0001	74409.20	1	44.04	< 0.0001
X₂ (Temperature)	0.016	1	6.49	0.0256	4.34	1	2.566 10^-3	0.9602
X ₃ (Time)	0.029	1	11.49	0.0054	20745.38	1	12.28	0.0027
X₄ (solvent:solid ratio)	0.012	1	4.62	0.0527
X₁X₄	0.012	1	4.87	0.0476
X₂X₃	0.42	1	168.59	< 0.0001
X₂X₄	0.024	1	9.51	0.0095
X₃X₄	0.45	1	182.08	< 0.0001
X₁ ²	0.31	1	125.39	< 0.0001
X₂ ²					14759.24	1	8.74	0.0089
Residual	0.030	12			28721.66	17
Lack of Fit	0.022	7	1.96	0.2386	22948.33	12		0.3013
Pure Error	8.009.10^-3	5			5773.33	5
Cor Total	2.44	21			1.386 10⁵	21
R²	0.9877				0.7928
R² _Adj	0.9785				0.7441
R² _Pred	0.9467				0.5957
PRESS	0.13				56047.29
Significant Model Terms	X ₁ , X ₂ , X ₃ , X ₁ X ₄ , X ₂ X ₃ , X ₂ X ₄ , X ₃ X ₄ , X ₁ ²				X ₁ , X ₃ , X ₂ ²
Second order polynomial equation by CCD-Optimal Responce Surface-after Backward Elimination	Y₁_HT =+0.17+0.34X₁+0.054X₂ +0.046X₃ +0.029X₄+0.061X₁X₄ -0.23X₂X₃ +0.084X₂X₄+0.24X₃X₄ +0.14X₁ ²				Y₂_TAA=+345.81+73.48X₁-0.57X₂ +38.99X₃ +31.28X₂ ²

	Method	Real values of independent variables X= [X₁,X₂,X₃,X₄]	Observed response values HT TAA	Predicted response value HT TAA
			(mg/g dw) (mM Trolox)	(mg/g dw) (mM Trolox)
MeOH/H ₂ O hydroalcoholic solvent extraction	Desirability (0.722)	[63.30 36.00 62.00 11.80]	0.809±0.110 451±2.32	0.820 455
EtOH/H ₂ O hydroalcoholic solvent extraction	Desirability (0.891)	[43.80 52.00 58.00 9.40]	0.175±0.004 297±0.817	0.179 298

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[1] Correspondence to: Nilüfer Vural E-mail: n.vural@ybu.edu.tr