Biochemical estimates
The biochemical components present in Toko fruit was recorded as per the various analysis done and the fruit was found to contain total sugar 3.33%, reducing sugar 1.76 mg/g, non reducing sugars 1.57 mg/g, total phenol content 2.82 mg/g, total flavonoids 2.01 mg/g, total anthocyanins 0.39 mg/g, protein 2.46 g/100 g and oil 27.27%. The appropriate composition of these components present in the fruits, make it suitable for consumption. The protein content of fruit is high which is similar to other minor fruits like Aegle marmelos Correa (2.20 g/100 g), Zizyphus mauritiana Lam (2.0 g/100 g) and Cordia myxa L (1.9 g/100 g) as described by Paul (2013). The antioxidant potential measured by FRAP and DPPH recorded was 134.21 mg/100g and 573.86 mg/100g, respectively, from fruit pulp of Livinstonia jenkinsiana (Table 1). Antioxidant potential of Toko fruit is 3 times higher than banana and mango (Shivashankara et al., 2020; Muralidhara et al., 2019).
Table 1
Biochemical estimation of Toko fruit (mg/g DW)
Parameters
|
Mean
|
Total Sugars
|
3.33 ± 0.23
|
Reducing Sugars
|
1.76 ± 0.06
|
Non-Reducing Sugars
|
1.57 ± 0.17
|
Total Phenols
|
2.89 ± 4.63
|
Total Flavonoids
|
2.06 ± 5.30
|
Total Anthocyanins
|
0.40 ± 3.05
|
FRAP
|
1.38 ± 4.55
|
DPPH
|
5.89 ± 2.53
|
Total Protein
|
24.61 ± 0.22
|
Oil (%)
|
27.15 ± 0.07
|
DW Dry weight; Data is expressed as (%) (mean value ± standard deviation) |
Fatty acid composition
A total of eleven fatty acids identified and quantified were lauric acid, linoleic acid, linolenic acid, margaric acid (heptadecanoic acid), myristic acid (tetradecanoic acid), oleic acid, palmitic acid (hexadecanoic acid), palmitoleic acid (9Z-hexadecanoic acid), pentadecanoic acid, stearic acid and tridecanoic acid. The percentage of each fatty acids quantified from the pulp is given in the Table 2.
Table 2
Fatty acid profiling of Toko fruit (%)
Fatty acids
|
Mean
|
Saturated fatty acids
|
5.89 ± 0.33
|
Unsaturated fatty acids
|
48.11 ± 0.33
|
Lauric acid/dodecanoic acid (C12:0)
|
0.18 ± 0.00
|
Linoleic acid (C18:2)
|
13.51 ± 0.16
|
Linolenic acid (C18:3)
|
2.48 ± 0.19
|
Margaric acid/heptadecanoic acid (C17:0)
|
3.30 ± 0.06
|
Myristic acid/tetradecanoate (C14:0)
|
0.18 ± 0.00
|
Oleic acid (C18:1)
|
32.86 ± 1.97
|
Palmitic acid/hexadecanoic acid (C16:0)
|
44.93 ± 1.54
|
Palmitoleic acid /(9Z)-hexadecenoic acid (C16:1)
|
0.17 ± 0.00
|
Pentadecanoic acid (C15:0)
|
0.19 ± 0.00
|
Stearic acid (C18:0)
|
2.02 ± 0.02
|
Tridecanoic acid (C13:0)
|
0.17 ± 0.00
|
Data is expressed as (%) (mean value ± standard deviation) |
The total saturated and unsaturated fatty acids present in the toko fruit pulp are 52.12 and 48.88%, respectively. The pulp is a rich source of palmitic acid (44.93%) followed by oleic acid (32.86%) and linoleic acid (13.51%) (Fig. 2), however, palmitoleic acid and tridecanoic acid (0.17%) recorded minimum. Such quantification of fatty acids were purely genetic makeup and was influenced by the climatic factors of the particular locality. Higher concentration of oleic acid, an omega-9 monounsaturated fatty acid present in the fruit pulp helps in reduction of blood pressure, cardiovascular risk by reducing cholesterol in the blood (Tere´ s et al. 2008; Lopez-Huertas 2010). Fruit has also a fair source of Linoleic acid (13.51%) a polyunsaturated omega-6 fatty acid possessing several health benefits such as, anti-diabetic, inhibition of breast cancer, retardation of atherosclerosis, helps in fat metabolism, and helps in enhancement of bone formation (Scimeca and Miller 2000).
Anthocyanins
A total of four anthocyanins were quantified viz., cyanidin, delphinidin malvidin, and pelargonidin. The quantified data of anthocyanins is presented in Table 3. The copper blue colour of the fruits is mainly due to the presence of malvidin (2032.64 µg/g) followed by delphinidin (124.25 µg/g) (Fig. 3). However, pelargonidin (0.38 µg/g) reported minimum. The glycosides of these anthocyanins have several health benefits such as, anti-oxidant, anti-obesity, anti-carcinogenic and antimicrobial properties (Khoo et al. 2017, Kumari et al. 2021).
Table 3
Anthocyanin profiling of Toko fruit (µg/g FW)
Anthocyanin
|
Mean
|
Cyanidin
|
30.98 ± 1.85
|
Delphinidin
|
124.25 ± 24.47
|
Malvidin
|
2032.64 ± 326.08
|
Pelargonidin
|
0.38 ± 0.04
|
Data is expressed as µg/g pulp fresh weight (mean value ± standard deviation) |
Organic acids
Eleven organic acids were quantified namely citric acid, fumaric acid, hydroxycitric acid, lactic acid, maleic acid, malic acid, malonic acid, pyruvic acid, shikimic acid, succinic acid and tartaric acid. The organic acids quantified are presented in the Table 4. The pulp of the toko fruit contains citric acid (3856.15 µg/g) as a predominant acid followed by malic acid (1654.90 µg/g) (Fig. 4). However, maleic acid (0.85 µg/g) was reported minimum. Citric acid which is present in the fruit, possess various health benefits and is known to decrease the DNA fragmentation, lipid peroxidation of brain and liver damage (Salam et al. 2014). Malic acid is widely used in the cosmetic industry as pH adjuster and skin conditioning humectants (Fiume 2001).
Table 4
Organic acids and sugars profiling of Toko fruit (µg/g FW)
Organic acid
|
Mean
|
Sugars
|
Mean (µg/g)
|
Citric acid
|
3856.15 ± 119.71
|
Arabinose
|
2.87 ± 0.47
|
Fumaric acid
|
1.60 ± 0.14
|
Fructose
|
158.73 ± 14.16
|
Hydroxycitric acid
|
27.35 ± 1.91
|
Fucose
|
5.46 ± 0.54
|
Lactic acid
|
10.95 ± 1.48
|
Galactose
|
5.57 ± 0.49
|
Maleic acid
|
0.85 ± 0.07
|
Glucose
|
89.67 ± 10.66
|
Malic acid
|
1654.90 ± 63.78
|
Inositol
|
20.21 ± 0.58
|
Malonic acid
|
165.90 ± 1.84
|
Lactose
|
0.70 ± 0.01
|
Pyruvic acid
|
31.40 ± 9.48
|
Maltose
|
0.24 ± 0.01
|
Shikimic acid
|
262.95 ± 12.09
|
Mannose
|
0.55 ± 0.04
|
Succinic acid
|
186.10 ± 6.22
|
Rhamnose
|
0.31 ± 0.06
|
Tartaric acid
|
2.75 ± 0.92
|
Ribose
|
0.72 ± 0.11
|
|
|
Sorbitol
|
19.25 ± 1.12
|
|
|
Sucrose
|
1.21 ± 0.00
|
|
|
Trehalose
|
0.06 ± 0.01
|
|
|
Xylose
|
1.39 ± 0.70
|
Data is expressed as µg/g pulp fresh weight (mean value ± standard deviation) |
Sugar profiling
Fifteen compounds of sugars namely, arabinose, fructose, fucose, galactose, glucose, inositol, lactose, maltose, mannose, rhamnose, ribose, sorbitol, sucrose, trehalose and xylose were identified and quantified. The quantified amounts of different sugars (µg/g fresh weight) are given in Table 4.
The major sugar present in the pulp of toko is fructose (158.73 µg/g) (Fig. 5) followed by glucose (89.67 µg/g), inositol (20.21 µg/g) and sorbitol (19.25 µg/g). However, trehalose was lowest (0.06 µg/g). Fruits of toko are not rich source of sugar. Fructose is the predominant sugar present in the fruit (0.15 mg/g) which is much lesser when compared with other fruits such as apple (76 mg/g), grapes (76 mg/g), banana (27 mg/g), cherry (62 mg/g) and vegetables like carrot (10mg/g) and tomato (14 mg/g) (Hallfrisch 1990). The presence of low sugar makes it as low glycemic index fruit, which helps in preventing various health complications such as cardiovascular disease and type 2 diabetes.
Phenolic acid profiling
A total of eighteen phenolic acids were identified and quantified viz., benzoic acid, caffeic acid, chlorogenic acid, ellagic acid, ferulic acid, gallic acid, gentisic acid, o-coumaric acid, p-coumaric acid, p-hydroxy benzoic acid, protocatechuic acid, salycylic acid, sinapic acid, syringic acid, t-cinnamic acid, vanillic acid, 2,4-dihydroxy benzoic acid and 3-hydroxy benzoic acid. The quantified amounts of the phenolic acids are given in the Table 5.
Table 5
Flavonoids and phenolic acids profiling of Toko fruit (µg/g FW)
Phenolic acid
|
Mean
|
Flavonoid
|
Mean
|
Chlorogenic acid
|
2.67 ± 0.21
|
Catechin
|
0.43 ± 0.09
|
Vanillic acid
|
3.82 ± 0.52
|
Umbelliferone
|
0.05 ± 0.01
|
Syringic acid
|
0.01 ± 0.00
|
Luteolin
|
5.63 ± 0.21
|
Ferulic acid
|
60.37 ± 4.87
|
Rutin
|
115.81 ± 6.28
|
Caffeic acid
|
3.39 ± 0.65
|
Hesperetin
|
0.55 ± 0.05
|
Gallic acid
|
0.33 ± 0.05
|
Myricetin
|
2.28 ± 0.17
|
p-Coumaric acid
|
3.01 ± 0.39
|
Quercetin
|
0.76 ± 0.09
|
o-Coumaric acid
|
3.70 ± 0.36
|
Apigenin
|
0.11 ± 0.00
|
2,4-Dihydroxy benzoic acid
|
3.82 ± 1.10
|
Naringenin
|
0.87 ± 0.04
|
Gentisic acid
|
660.75 ± 3.05
|
Kaempferol
|
0.01 ± 0.00
|
Protocatechuic acid
|
27.81 ± 4.02
|
Epicatechin
|
8.74 ± 0.28
|
t-Cinnamic acid
|
0.68 ± 0.03
|
Epigallocatechin
|
2.42 ± 0.26
|
p-Hydroxy benzoic acid
|
1.07 ± 0.01
|
Galangin
|
0.03 ± 0.00
|
Salycylic acid
|
2.51 ± 0.13
|
|
|
Benzoic acid
|
0.01 ± 0.00
|
|
|
3-Hydroxy benzoic acid
|
1.34 ± 0.15
|
|
|
Sinapic acid
|
0.38 ± 0.09
|
|
|
Ellagic acid
|
0.08 ± 0.00
|
|
|
Data is expressed as µg/g pulp fresh weight (mean value ± standard deviation) |
Major phenolic acid present in the toko fruit was recorded as gentisic acid (660.75 µg/g) (Fig. 6) followed by ferulic acid (60.37 µg/ g), whereas, ellagic acid (0.08 µg/g) reported the minimum. Gentisic acid is having various health benefits such as antigenotoxic, anti-inflammatory, antimicrobial, hepatoprotective, neuroprotective, and especially a potential antioxidant. The gentisic acid is having a potential free radical scavenging action and inhibits the low density lipoprotein oxidation with a minimum chelating effect (Ashidate et al. 2005). It is an important metabolite of aspirin which widely occurs in plants as a secondary metabolite. Besides toko fruit, gentisic acid is also found in fruits such as apple, avocados, black berries, kiwi fruits, pears, some mushrooms and other plant species such as Citrus spp., Gentiana spp., Helianthus tuberosus, Hibiscus rosa-sinensis, Olea europaea, Pterocarpus santalinus, Sesamum indicum and Vitis vinifera (Abedi et al., 2020). Ferulic acid is considered to have many physiological functions, including anticarcinogenic, anti‐inflammatory, antimicrobial, antioxidant and anti‐thrombosis activities. It is widely found in fruits and vegeTables and some medicinal herbs viz., Angelica sinensis, Cimicifuga racemosa, and Ligusticum chuangxiong. It is having wide application in cosmetic and food industries because of its low toxicity (Ou et al. 2004; de Oliveira Silva and Batista 2017).
Flavonoid composition
A total of thirteen flavonoid compounds were identified and quantified. The compounds identified were apigenin, catechin, epicatechin, epigallocatechin, galangin, hesperetin, kaempferol, leutolin, myricetin, naringenin, quercetin, rutin and umbelliferone. The quantified compounds (µg/g) present in fruit pulp are given in Table 5.
The predominant flavonoid present in the pulp of toko fruit is rutin (115.81 µg/g) (Fig. 7) whereas; kaempferol (0.01 µg/g) was reported minimum. Chemically rutin is a glycoside that comprises of flavonolic aglycone quercetin and disaccharide rutinose. It is having a number of pharmacological properties, including anticarcinogenic, antimicrobial, antioxidant, cardioprotective, cytoprotective, neuroprotective and vasoprotective activities (Ganeshpurkar and saluja 2017; Javed et al. 2012; Richetti et al. 2011; Nassiri-Asl et al. 2010).