Phenolic profile and antioxidant activity of thermally processed sponge gourd (Luffa cylindrica) as studied by using high performance thin layer chromatography (HPTLC)

Figures & data

Table 1. Phytochemical screening of the extracts of Luffa cylindrica.

Samples	Treatments	Flavonoids			Tannin			Saponin			Terpenoids			Alkaloids
		ME	EE	BE	ME	EE	BE	ME	EE	BE	ME	EE	BE	ME	EE	BE
L. cylindrica
	Raw	+	+	+	^−	+	^−	+	+	^−	+	+	+	+	+	^−
	Pressure Cooked	+	+	+	+	+	^−	+	+	^−	+	^−	+	+	^−	+
	Microwave Cooked	^−	^−	+	^−	+	+	++	+	^−	+	+	+	^−	^−	+
	Fried	++	++	++	+	+	+	^−	^−	^−	+	^−	^−	^−	+	+

^{+ Present moderately, ++ present strongly, − Absent; ME – methanolic extract, EE – ethanolic extract, BE – butanolic extract.}

Table 2. Total phenols, flavonoids, tannins, and carotenoid contents of various extracts of differently cooked L. cylindrica.

Treatments	Total phenols (mg GE/100g)				Total flavonoids (mg QE/100g)				Tannin content (mg CE/100g)					Carotenoid content (mg β- Carotene/100g)
	ME	EE	BE	Mean	ME	EE	BE	Mean	ME	EE	BE	Mean	ME	EE	BE	Mean
Raw (control)	216.4 ± 2.1^aA	300.1 ± 2.5^bC	275.1 ± 2.6^cB	263.8^b	24.6 ± 0.45^bA	45.5 ± 0.7^bB	146.4 ± 0.8^cC	72.1^b	29.4 ± 1.6^cB	25.0 ± 2.23^cB	17.9 ± 2.4^bA	24.1^b	4.6 ± 0.1^aA	10.0 ± 0.2^aB	12.9 ± 0.2^aC	9.2^a
Pressure cooked	339.4 ± 4.2^bC	311.01 ± 5.6^cB	258.7 ± 3.9^bA	303.0^c	68.7 ± 1.0^cB	55.8 ± 1.7^cA	136.6 ± 0.9^bC	87.0^c	17.5 ± 4.3^bB	9.7 ± 5.4^aA	9.4 ± 3.9^aA	12.1^a	11.0 ± 0.2^cA	12.4 ± 0.2^bB	31.3 ± 0.2^dC	18.2^d
Microwave cooked	219.6 ± 2.4^aC	207.2 ± 3.0^aB	178.7 ± 2.6^aA	201.8^a	19.3 ± 0.67^aA	24.4 ± 0.8^aB	86.4 ± 0.6^aC	43.4^a	6.0 ± 2.5^aA	17.0 ± 3.2^bB	16.5 ± 2.2^bB	13.1^a	6.0 ± 0.1^bA	16.9 ± 0.2^cB	22.2 ± 0.1^cC	15.0^b
Fried	368.6 ± 4.8^cA	441.9 ± 2.7^dB	490.3 ± 2.9^dC	433.6^d	255.9 ± 0.9^dB	249.3 ± 1.6^dA	282.7 ± 0.6^dC	262.7^d	9.6 ± 4.0^aA	17.9 ± 2.6^bB	17.0 ± 2.4^bB	14.8^a	14.7 ± 0.2^dA	17.0 ± 0.2^cB	19.7 ± 0.1^bC	17.1^c
Mean	286.0^A	315.1^C	300.7^B		92.1^A	93.8^B	163.0^C		15.6^A	17.4^A	15.2^A		9.1^A	14.1^B	21.5^C
^F-Statistics for extraction solvents = 216 at df = 2, p = 0.000					^F-Statistics for extraction solvents = 20822.3 at df = 2, p = 0.000				^F-Statistics for extraction solvents = 1.5 at df = 2, p = 0.232				^F-Statistics for extraction solvents = 16274.4 at df = 2, p = 0.000
^F-Statistics for cooking treatments = 7753.4 at df = 3, p = 0.000					^F-Statistics for cooking treatments = 93918.3 at df = 3, p = 0.000				^F-Statistics for cooking treatments = 25.4 at df = 3, p = 0.01				^F-Statistics for cooking treatments = 5039.1 at df = 3, p = 0.000
^F-Statistics for cooking treatments & extraction solvents = 585.1 at df = 6, p = 0.000					^F-Statistics for cooking treatments & extraction solvents = 1360.1 at df = 6, p = 0.000				^F-Statistics for cooking treatments & extraction solvents = 10.2 at df = 6, p = 0.000				^F-Statistics for cooking treatments & extraction solvents = 2206.3 at df = 6, p = 0.000

^{Values are presented as mean ± SD (n = 3) and referred to the dry weight.}

^{Small and capital letters in superscripts indicate significant differences (p < 0.05) among cooking methods and extracts respectively}

^{GE = gallic acid equivalent, QE = quercetin equivalent, CE = catechin equivalent}

^{ME = methanolic extract, EE = ethanolic extract, BE = butanolic extract.}

Table 3. Antioxidant activity of various extracts of differently cooked vegetable of L. cylindrica as determined by FTC, TBA, and FRAP assays.

Treatment	FTC(% Inhibition)				TBA (% Inhibition)				FRAP μM FeSO4/100g
	ME	EE	BE	Mean	ME	EE	BE	Mean	ME	EE	BE	Mean
Raw (Control)	14.7 ± 0.6^bA	17.9 ± 0.5^bB	18.6 ± 0.9^bB	17.1^b	26.7 ± 0.4^bB	29.0 ± 0.4^bC	25.8 ± 0.4^bA	27.2^b	751.4 ± 12.8^bA	1607.9 ± 17.2^cC	828.7 ± 18.5^bB	1062.7^b
Pressure cooked	39.6 ± 0.7^dC	18.6 ± 0.6^bB	6.3 ± 0.5^aA	21.5^c	48.5 ± 0.5^dC	29.9 ± 0.4^cB	18.9 ± 0.4^aA	32.4^c	1133.4 ± 38.8^cB	1210.5 ± 44.1^bC	792.4 ± 38.5^abA	1045.5^b
Microwave cooked	12.8 ± 0.8^a B	15.6 ± 0.5^aC	6.1 ± 0.9^aA	11.5^a	24.8 ± 0.5^aB	27.3 ± 0.4^aC	19.5 ± 0.4^aA	23.9^a	407.9 ± 19.7^aA	557.6 ± 26.3^aB	776.5 ± 19.8^aC	580.7^ab
Fried	35.4 ± 0.9^c C	28.6 ± 0.5^cB	26.3 ± 0.7^c A	30.1^d	44.6 ± 0.4^cB	38.9 ± 0.4^dA	38.6 ± 0.4^cA	40.7^d	1329.4 ± 30.6^dA	1876.0 ± 22.0^dB	2022.4 ± 30.3^cC	1742.6^c
Mean	25.6^C	20.2^B	14.3^A		36.1^C	31.3^B	25.7^A		905.5^A	1313.0^C	1105.0^B
^F-Statistics for extraction solvents = 777.1 at df = 2,					^F-Statistics for extraction solvents = 1921.2 at df = 2,				^F-Statistics for extraction solvents = 626.1 at df = 2,
^p = 0.000					^p = 0.000				^p = 0.000
^F-Statistics for cooking treatments = 1121.5 at df = 3,					^F-Statistics for cooking treatments = 2844.5 at df = 3,				^F-Statistics for cooking treatments = 2590 at df = 3,
^p = 0.000					^p = 0.000				^p = 0.000
^F-Statistics for cooking treatments & extraction solvents = 417.6 at df = 6, p = 0.000					^F-Statistics for cooking treatments & extraction solvents = 843.9 at df = 6, p = 0.000				^F-Statistics for cooking treatments & extraction solvents = 346.5 at df = 6, p = 0.000

^{Values are presented as mean ± SD (n = 3) and referred to the dry weight.}

^{Small and capital letters in superscripts indicate significant differences (p < 0.05) among cooking methods and extracts respectively.}

^{FTC % Inhibition of BHT = 88.8 ± 0.28, Vit. E = 74.6 ± 0.16.}

^{TBA % Inhibition of BHT = 90.9 ± 0.47, Vit. E = 78.3 ± 0.19.}

^{ME = methanolic extract, EE = ethanolic extract, BE = butanolic extract.}

Table 4. Free radical scavenging activity of various extracts of cooked vegetable of L. Cylindrica as measured by DPPH assay.

	DPPH (% Scavenging at 30 µg/ml)					IC-50 (µg/ml)
	ME	EE	BE	Mean	ME	EE	BE	Mean
Raw (Control)	20.5 ± 0.2^dC	9.6 ± 0.1^dB	6.2 ± 0.1^bA	12.1^b	147.3	200.4	171.8	173.2
Pressure cooked	8.1 ± 0.6^bA	11.9 ± 0.7^cB	16.8 ± 0.2^cC	12.3^b	237.4	132.2	75.7	148.4
Microwave cooked	12.4 ± 0.3^cA	19.1 ± 0.1^dB	29.8 ± 1.2^dC	20.5^c	108.4	84.7	51.3	81.5
Fried	5.4 ± 0.1^aB	7.4 ± 0.2^aC	4.4 ± 0.2^aA	5.7^a	357.5	240.3	503.5	367.1
Mean	11.6^A	12.0^B	14.3^A		212.6	164.4	200.5
^All data are reported as mean ± SD (n = 3)
^F-Statistics for extraction solvents = 133.4 at df = 2, p = 0.000
^F-Statistics for cooking treatments = 1693.3 at df = 3, p = 0.000
^F-Statistics for cooking treatments and extraction solvents = 751.8 at df = 6, p = 0.000
^% Scavenging of ascorbic acid at 30 μg/ml = 92.0 ± 0.06

^{Small and capital letters in superscripts indicate significant differences (p < 0.05) among cooking methods and extracts, respectively.}

^{ME = methanolic extract, EE = ethanolic extract, BE = butanolic extract.}

^IC₅₀^{value of ascorbic acid = 5.05 μg/ml.}

Table 5. Identification and quantification of phenolic acids and flavonoids (μg/ml of extract) in ME as determined by HPTLC.

Compounds	Raw	Pressure Cooked	Microwave cooked	Fried
Phenolic acids
Gallic acid	26.85	nd	nd	nd
Caffeic acid	18.43	6.87	1.04	0.23
Chlorogenic acid	nd	nd	nd	nd
p-Coumaric acid	nd	nd	nd	nd
Vanillic acid	nd	nd	nd	nd
Ferulic acid	49.62	9.31	27.22	nd
Cinnamic acid	8.63	7.74	6.50	1.52
Benzoic acid	nd	nd	nd	nd
Ellagic acid	nd	78.84	nd	nd
Flavonoids
Quercetin	nd	nd	55.42	45.18
Myrecetin	35.79	nd	20.95	30.89
Apigenin	nd	nd	nd	nd
Kaempferol	nd	nd	nd	nd
Leutolin	nd	nd	nd	nd
Rutin	nd	79.32	nd	nd
Catechin	nd	62.24	77.87	57.94

^{nd = not detected.}

Figure 1. HPTLC profile of ME of L. cylindrica as developed in chloroform: hexane: methanol: formic acid (6.4: 3.9: 2.0: 0.5) (a) raw, (b) pressure cooked, (c) microwave cooked, and (d) fried.

Figure 2. HPTLC profile of ME of L. cylindrica as developed in chloroform: hexane: methanol: formic acid (4.0: 1.0: 1.0: 1.0) (a) raw, (b) pressure cooked, (c) microwave cooked, and (d) fried.

Figure 3. HPTLC profile of ME of L. cylindrica as developed in acetonitrile: methanol: water (4.5: 1.0: 0.5) (a) raw, (b) pressure cooked, (c) microwave cooked, and (d) fried.

Table 6. Pearson correlation coefficients (r) between phytochemicals and antioxidant activity.

	Phenols	Flavonoids	Tannin	Carotenoids	FTC	TBA	FRAP	DPPH
Phenols	1.000
Flavonoids	.811**	1.000
Tannin	.365	.296	1.000
Carotenoids	.117	.437	.443	1.000
FTC	.711**	.471	.317	−.271	1.000
TBA	.737**	.478	.378	−.241	.989*	1.000
FRAP	.909**	.702*	.378	.119	.562	.600*	1.000
DPPH	.880**	.756**	.224	−.039	.712**	.740**	.783**	1.000

^{*Significantly correlated at p < 0.05, n = 12.}

^{** Significantly correlated at p < 0.01, n = 12.}