Evaluation of extraction protocols for anti-diabetic phytochemical substances from medicinal plants

Table 1 Comparison of percentage recovery yield, extraction time and volume of solvent used for the different extraction methods for the two plants

	Vernonia amygdalina			Ocimum gratissimum
Parameter	MAE	Soxhlet	Maceration	MAE	Soxhlet	Maceration
Sample (g)	50	50	50	50	50	50
Solvent volume (mL)	250	500	900	250	500	900
Extraction time (min)	39	265	4320	39	255	4320
Recovery yield (g)	10.45 ± 0.53b	7.88 ± 0.35a	7.18 ± 0.14a	9.55 ± 0.84b	5.63 ± 0.21a	5.08 ± 0.32a
Percentage recovered (%)	20.90 ± 1.05b	15.75 ± 0.71a	14.35 ± 0.28a	19.10 ± 1.67b	11.25 ± 0.24a	10.15 ± 0.65a

Values are mean ± SD of 3 replicate determinations; same superscript across the column under the same plant indicate no significant difference (P > 0.05). MAE: Microwave-assisted-extraction.

Table 2 Calculated percentage differences in recovery yield of extracts between the extraction methods

Vernonia amygdalina	Ocimum gratissimum
	MAE	Soxhlet	Maceration
MAE		41.05%	46.81%
Soxhlet	24.59%		9.77%
Maceration	31.29%	8.88%

Percentage difference between two extraction methods = [(values from method with higher recovery yield - values from method with lower recovery yield)/values from method with higher recovery yield] × 100.

Table 3 Comparison of some qualitative phytochemicals obtained with the three extraction methods for the two plants

S/N	Constituents	Maceration		Soxhlet		Microwave
		VA	OG	VA	OG	VA	OG
1	Carbohydrates	+	+	+	+	+	+
2	Anthraquinones	-	-	-	-	-	-
3	Glycosides	+	+	+	+	+	+
4	Cardiac glycosides	+	+	+	+	+	+
5	Saponins	+	+	+	+	+	+
6	Steroids	+	+	+	+	+	+
7	Triterpenes	+	+	+	+	+	+
8	Tannins	+	+	+	+	+	+
9	Flavonoids	+	+	+	+	+	+
10	Alkaloid	+	+	+	+	+	+

The symbol (+): Indicate detected; (-): Not detected; VA: Vernonia amygdalina; OG: Ocimum gratisimum.

Table 4 Comparison of the quantitative phytochemicals obtained with the three extraction methods for the two plants

	Vernonia amygdalina (mg/100 g)			Ocimum gratissimum (mg/100 g)
	MAE	Soxhlet	Maceration	MAE	Soxhlet	Maceration
Alkaloid	4.0 ± 0.65a	7.0 ± 0.57b	5.0 ± 0.46a	6.5 ± 0.75b	7.0 ± 0.15b	5.0 ± 0.90a
Flavonoid	13.0 ± 0.35b	9.0 ± 0.50a	15.0 ± 0.21c	10.0 ± 0.35b	8.0 ± 0.18a	12.0 ± 0.25c
Phenolic	17.5 ± 0.25c	15.0 ± 0.21b	12.0 ± 0.70a	15.0 ± 0.22c	14.0 ± 0.21b	11.0 ± 0.65a
Saponin	4.5 ± 0.45b	3.0 ± 0.30a	2.0 ± 0.75a	6.1 ± 0.75b	4.0 ± 0.92a	5.0 ± 0.20a
Tannin	14.0 ± 0.55b	13.0 ± 0.50b	10.0 ± 0.25a	12.0 ± 0.18b	9.0 ± 0.24a	9.1 ± 0.25a

Values are mean ± SD of 3 replicate readings. Same superscript across the column under the same plant signifies no significant difference at P > 0.05. MAE: Microwave-assisted-extraction.

Table 5 Effect of the extract from the different extraction methods on blood glucose in streptozotocin-induced diabetic rats

Group	Before induction	7 d after induction	Days after treatment
			7th	14th	21st
CME	79.4 ± 4.5	344.6 ± 10.3	282.8 ± 17.6	195.8 ± 18.3	106.5 ± 6.7
SEE	85.3 ± 3.2	396.8 ± 15.7	342.5 ± 14.7	264.9 ± 16.8	121.1 ± 10.2
MAE	82.7 ± 5.1	373.3 ± 13.6	331.3 ± 11.4	237.1 ± 8.9	102.4 ± 7.6
PC	91.6 ± 4.5	389.4 ± 11.9	359.0 ± 12.6	266.3 ± 13.2	97.3 ± 5.8
NC	80.6 ± 3.8	365.5 ± 9.8	395.1 ± 16.3	419.6 ± 10.2	448.4 ± 17.4
HC	83.2 ± 6.2	84.8 ± 4.7	83.9 ± 7.8	84.7 ± 6.5	84.2 ± 7.1

Values are mean ± SD (mg/dL) of readings from 6 rats per group. CME: Cold maceration extract; SEE: Soxhlet extraction extract; MAE: Microwave-assisted extraction extract; PC: Positive control; NC: Negative control; HC: Healthy control.

Table 6 Calculated percentage change in blood glucose after treatment with the extracts in streptozotocin-induced diabetic rats

Group	Initial blood glucose on day 0 (mg/dL)	Percentage change after treatment (%)
		Day 7	Day 14	Day 21
CME	344.6 ± 10.3	18.0 ± 2.66e	43.3 ± 3.62e	69.1 ± 1.03c
SEE	396.8 ± 15.7	13.7 ± 0.29d	33.3 ± 1.60c,d	69.5 ± 0.71c
MAE	373.3 ± 13.6	11.2 ± 0.18c,d	36.5 ± 0.08d	72.6 ± 1.03d
PC	389.4 ± 11.9	7.8 ± 0.42c	31.6 ± 1.30c	75.0 ± 0.73d
NC	365.5 ± 9.8	-8.1 ± 1.57a	-14.8 ± 0.29a	-22.7 ± 1.47a
HC	84.8 ± 4.7	1.4 ± 3.96b	0.1 ± 2.12b	0.7 ± 2.88b

Same superscript down the column signifies no significant difference at P > 0.05. Percentage change in blood glucose = [(blood glucose before treatment - blood glucose after treatment)/blood glucose before treatment] × 100. CME: Cold maceration extract; SEE: Soxhlet extraction extract; MAE: Microwave-Assisted Extraction extract; PC: Positive control; NC: Negative control; HC: Healthy control.