Seed Waste from Custard Apple | Encyclopedia MDPI

Seed Waste from Custard Apple: Comparison

Please note this is a comparison between Version 1 by Nadeem Rais and Version 2 by Peter Tang.

Annona squamosa L. (custard apple or sugar apple), belonging to the Annonaceae family, is a small tree or shrub that grows natively in subtropical and tropical regions. Seeds of the custard apple have been employed in folk medicines because of the presence of bioactive chemicals/compounds such as alkaloids, flavonoids and phenolic compounds and acetogenins and cyclopeptides that are responsible for various biological activities. The seeds also show the presence of tannins, vitamin C, vitamin E and a higher content of amino acids. From investigations, it has been shown that the seeds of A. squamosa have considerable potential to be used as an antibacterial, hepatoprotective, antioxidant and antitumor/anticancer agent. Cyclosquamosin B, extracted from the custard apple seed, possesses vasorelaxant properties. Tocopherols and fatty acids, notably oleic acid and linoleic acid, are also found in the seed oil. A. squamosa seeds contain a high amount of annonaceous acetogenins compounds, which are potent mitochondrial complex I inhibitors and have high cytotoxicity. A survey primarily based on the nutritional, phytochemical and biological properties showed that A. squamosa seeds can be used for the discovery of novel products, including pharmaceutical drugs.

custard apple seed
health benefits
bioactivities
phytochemistry
anticancer

1. Introduction

Annona squamosa L. belongs to the Annonaceae family, a tropical fruit tree endemic to South and Central America, West Indies, Brazil, India, Egypt, Peru and Bermuda. In India, A. squamosa is widely cultivated in various states, including Assam, Uttar Pradesh, Bihar, Chhattisgarh, Maharashtra, Madhya Pradesh, Tamil Nadu, etc., for its edible fruit [1]. It is a small semi-deciduous branched tree or shrub that can reach up to 3–8 m in height and its fruits and seed by-product is shown in Figure 1 [2]. Since ancient times, A. squamosa has been utilized in folk medicines and in various other applications involving food product development, e.g., the fruit pulp is used as a juice or as a flavoring agent. Custard apple industrial processing units generate large amounts of seeds, peels or seed coats [2]. The seeds are underutilized as the non-edible part of the fruit is discarded as waste, i.e., seed waste. The custard apple waste (seed) has a range of useful bioactive compounds ^[1][2][3][1,2,3]. Thus, seeds may potentially be extracted and may produce considerable income for the food processing industries. In India, the seeds have been used to make a hair tonic to remove headlice ^[1][3][1,3]. Ground seeds soaked in water have been used as an insecticide, a poison for fish, a strong eye irritant and a way to induce abortions ^[4][5][6][4,5,6]. Recent studies have shown that different parts of the plants, i.e., seeds, leaves, husks, peels and seed coats that are left after the main harvesting, are a rich source of phytochemicals and nutrients and can be utilized for novel product development, including usage in the food and pharmaceutical industries ^[1][7][1,7]. More than 400 active compounds have been isolated from A. squamosa [8]. In recent years, studies related to the pharmacological and phytochemical activities of A. squamosa seeds have confirmed that the major active chemical constituents are annonaceous acetogenins and cyclopeptides ^[9][10][9,10]. Annonaceous acetogenins, a class of polyketides, containing oxygenated functional groups including ketones, epoxides, hydroxyls, tetrahydropyrans and tetrahydrofurans, essentially found in the seeds, have been shown to have strong antibacterial, anti-ovulatory, anti-inflammatory, antithyroidal and other properties ^[11][12][13][11,12,13]. In vivo studies show that seed extracts of A. squamosa are beneficial for treating liver cancer, prostate cancer, cervical cancer, pancreatic cancer, etc. ^[12][14][12,14]. The biological activities exhibited by A. squamosa seed extract are caused mainly because of phenolic compounds, alkaloids, peptides, amino acids, sterols, tannins, flavonoids, polysaccharides and tocopherols present in it ^[12][15][16][12,15,16]. Interestingly, annonaceous acetogenins extracted from custard apple seeds possess antitumor/anticancer activity ^[12][17][12,17]. These compounds proved to be cytotoxic against various cancer cell lines. For example, a volatile compound, namely bullatacin, isolated from the seed oil of A. squamosa is involved in antitumor activity [18]; the aqueous and organic seed extract of A. squamosa induced apoptosis of tumor cell death with the enhanced activity of caspase-3 and the down-regulation of antiapoptotic genes Bcl-2 and Bcl-xL when treated with organic seed extract and both seed extracts, respectively [11]; petroleum ether seed extract shows inhibition of keratinocyte (HaCaT cells) proliferation [19]. Processes 10 02119 g001 550

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Figure 1.

Custard apple fruit and its seed by-products.

2. Proximate Composition of Custard Apple Seeds

The fresh fruits of A. squamosa are commonly eaten in various regions of India, but the seed oil has not been reported yet for edible purposes. The seed of the custard apple is mainly composed of a seed coat (32.4%) and a seed kernel (67.7%). On a dry weight basis, the investigation shows a 22.2% content of crude fatty oil in seed kernels. The method of gas chromatography–mass spectroscopy (GC/MS) was used for studying the methyl esters of custard apple seed’s fatty oil to determine its chemical composition, and results showed a total of 11 fatty acids, among which linoleic acid (22.9%), oleic acid (47.4%), palmitic acid (12.1%) and stearic acid (13.6%) were present in higher amounts. 11-eicosanoic acid (0.2%), dihydro sterculic acid (0.1%), eicosanoic acid (0.9%), heneicosanoic acid (2.3%) and margaric acid (0.2%) were all found in lesser amounts in the oil. These 11 fatty acids together constitute nearly 99.8% of the oil. 17-methyloctadecanoic acid (0.1%) and palmitoleic acid (0.01%) were both identified in traces or in a minimum amount. The high quantity of unsaturated fatty acids (UFAs) was also determined in further investigations of the oil. About 70.3% of the oil was contributed by linoleic acid (22.9%) and oleic acid (47.4%); similarly, 25.7% of the oil consisted of palmitic acid (12.1%) and stearic acid (13.6%) ^[20][21]. Mariod et al., ^[21][22] have demonstrated the presence of leucine, isoleucine, glutamic acid, phenylalanine-tyrosine, aspartic acid, serine, alanine, methionine-cystine, histidine, arginine, glycine, valine, threonine and lysine in the amounts of 0.845, 0.464, 0.995, 0.671, 0.684, 0.299, 0.594, 0.106, 0.139, 0.704, 0.392, 0.642, 0.324 and 0.407 g/100g protein, respectively ^[21][22]. A proximate composition analysis of A. squamosa seeds demonstrated the presence of carbohydrate, fat, fiber, ash, protein and moisture at concentrations of 66.64, 29.21, 32.64, 1.90, 2.25 and 3.92 g/100g dry weight (DW) (%), respectively ^[22][23]. On the other hand, minerals (in mg/kg) such as K (56.47%) and Ca (46.90%) are present in higher amounts compared with P (33.30%), Mg (20.36%), Fe (6.74%), Cu (0.30%), Na (9.29%), Zn (0.43%) and Mn (0.25%) ^[22][23] (Table 1). By comparing the results of Shehata et al., ^[22][23] with other reference studies ^[23][24][24,25], it was concluded that the presence of a higher Ca content is important for healthy teeth and bones, while Fe is essential for preventing anemia. Minerals are also responsible for maintaining pH levels and blood pressure in the human body ^[25][26].

Table 1.

Proximate composition of

Annona squamosa

seeds.

Variety	Category	Compound	Yield/Concentration	Ref.
Annona squamosa seeds		Fatty acids (%)		Antimicrobial Margaric acid	Chloroform extract of seeds (10–60 μg/mL) 0.2	E. coli, S. typhi, K. pnemoniae, P. mirabilis,	^[20][21]
	B. subtilis		,	S. aureus		Significant antibacterial activity with inhibition rate of 37–56, 40–60.75, 36–64, 48.5–63, 35–53.5 and 34–47% for K. pneumoniae, B. subtilis, E. coli, P. mirabilis, S. typhi and S. aureus		^[44][45]	Linoleic acid
	Annona squamosa seeds		22.9
	(Nashik, Maharashtra)		Antimicrobial	Petroleum ether, methanol and chloroform seed extract	E. coli, P. aeruginosa, S. aureus, K. pneumoniae, B. subtilis	PEE: highest growth inhibition rate was observed for S. aureus (ZOI: 12 mm) and lowest for P. aeruginosa with (ZOI 7.8 mm); ME: significant inhibition against K. pneumoniae (ZOI: 12.8 mm) and B. subtilis (ZOI: 9.2 mm); CE: inhibition against E. coli (ZOI: 14.8 mm) and B. subtilis (ZOI: 1.7 mm)		^[45][46]	Eicosanoic acid
	Annona squamosa seeds		0.9
	(Jayanagar, Bangalore)		Antimicrobial	Methanolic seed extract (50 mg/mL)	E. coli, S. typhi, S. aeurus, E. faecalis, P. aeruginosa, S. paratyphi, K. pneumoniae	Inhibits growth of bacterial strains with ZOI equal to 27–30 mm for E. coli, 31 mm for S. typhi, 27–32 mm for S. aeurus, 23 mm for E. faecalis, 22–24 mm for P. aeruginosa, 22–30 mm for S. paratyphi, 11–20 mm for K. pneumoniae		^[46][47]	Palmitic acid
	Annona squamosa seeds (Bangalore)		12.1
			Antimicrobial	Methanolic seed extracts of A. squamosa and Prunus Persia (1:2)	S. aureus, E. coli, K. pneumoniae, S. typhi, Enterococcus faecalis, P. aeruginosa, S. paratyphi	ZOI ranges between 18–34 mm for all tested pathogens		^[47][48]	Heneicosanoic acid	2.3
	Annona squamosa seeds (Alexandria, Egypt)		Antimicrobial	-	E. coli, C. albicans, B. subtilis, K. pneumoniae, S. senftenberg, S. aureus	ZOI ranging between 9.50, 9.53, 10.33, 12.30 6.50 and 12.50 mm against E. coli, C. albicans, K. pneumoniae, S. senftenberg, S. aureus and B. subtilis, respectively		^[22][23]	Stearic acid	13.6
	Annona squamosa seeds		Antimicrobial	Aqueous seed extract (500 and 1000 mg pm- CuO NPs)	Xanthomonas oryzae	At 500 mg: ZOI = 9 mm; at 1000 mg: ZOI = 15 mm		^[48][49]	Oleic acid	47.4
	Annona squamosa seeds (Nam Dinh, Vietnam)		Antifungal	Acetogenins (squamostatin-A (7), squamocin-G (5), and squamocin (8)) extracted from custard apple seeds	Phytophthora infestans	Acetogenins exhibit dose-dependent activity against the growth of zoospore and sporangium IC₅₀ value for inhibition of sporangium germination was 1.24–2.09 μg/mL and IC₅₀ value for zoospore germination inhibition was 1.89–3.05 μg/mL, for all acetogenins		^[49][81]	11-eicosanoic acid	0.2
Annona squamosa seeds	Antidiabetic	Ethanolic and methanolic seed extract (200 mg/kg BW)	Alloxan-induced diabetic rats	Decrease in level of blood glucose after administration of ethanolic seed extract (139.8–142 mg/dL) and methanolic seed extract (139–146 mg/dL) at 7th day of treatment	^[50][52]	Dihydrosterculic acid	0.1
Annona squamosa seeds	Anti-inflammatory	Cyclopeptides-met-cherimolacyclopeptide and cyclosquamosin D (A₁), and B (B)	LPS-J774A.1 cell line	Reduction in IL-6 and TNF-α secretion in J774A with an IC₅₀ value of 1.22 and 9.2 µM	^[51][56]	17-Methyloctadecanoic acid
Annona squamosa seeds (Luye, Taitung County, Taiwan)	0.1
	Anti-inflammatory	Cyclosquamosin D	Lipopolysaccharide and Pam3Cys-stimulated J774A.1 macrophages	Inhibition of secretion of pro-inflammatory cytokines	^[52][57]	Palmitoleic acid
Annona squamosa seeds (Jiangsu, China)	0.01
	Antitumor	Bullatacin and 12,15-cis-squamostatin-A	A-549, Hela, HepG2 and MCF-7 (in vitro) and H₂₂ tumor cell line in mice (in vivo)	IC₅₀ value for MCF-7, A-549, and HepG2 and Hela, are 2.5 × 10⁻¹, 3.2, 3.6 × 10⁻¹ and 13.0 µg/mL, respectively, and 69.55% inhibition of H₂₂ cell line	[18]	Annona squamosa seeds
Annona squamosa seeds (Jiangsu, China)	Amino acids (g/100 g protein)	Leucine	0.845	Antitumor	^[21		Seed oil	H₂₂ tumor cell line (mice: in vivo)	^][22]
		Inhibition of growth of H	₂₂	cell line with maximum inhibitory rate of 53.54%				^[53][62]		Isoleucine	0.464
Annona squamosa seeds (TaiDong County, Taiwan)		Antitumor	Squadiolins A and B and squafosacin B	MDA-MB-231, Hep G2, MCF-7 and Hep 3B, cell lines			Squadiolins A- MDA-MB-231: IC₅₀ = 0.63 µM; squadiolins B- MDA-MB-231: IC₅₀ = 0.28 µM; squafosacin B- HepG2: IC₅₀ = 0.71 µM; Hep 3B: IC₅₀ = 0.72 µM; MCF-7: IC₅₀ = 0.96 µM	^[54][63]		Glutamic acid
Annona squamosa seeds (Hyderabad, India)		0.995
		Antitumor	Aqueous and organic extract from defatted seeds	AK-5 histiocytic tumor cell line in rat animal model			Significant tumor cell apoptosis, with increased caspase-3 expression, down regulation of Bcl-2 and Bclxl antiapoptotic genes	[11]		Phenylalanine + Tyrosine
Annona squamosa seeds (Beijing, China)		0.671
		Anticancer	Seed oil nanoparticles	4T1-Mouse breast cancer cells			Inhibitory rate of 69.8% against 4T1 cell line	^[55][64]		Aspartic acid
Annona squamosa seeds		0.684
		Anticancer	Ethanolic seed extract	MCF-7 breast cancer cell line			Inhibit growth of MCF-7 (IC₅₀ = 10 ug/mL) by inducing apoptosis	^[56][82]		Serine
Annona squamosa seeds (Alexandria, Egypt)		0.299
		Anticancer	-	HepG-2, MCF-7, Caco-2 and PC-3 cancer cell lines			Caco-2: IC₅₀ = 11.55 μg/mL; HepG-2: IC₅₀ = 7.99 μg/mL; MCF-7: IC₅₀ = 14.34 μg/mL; PC-3: IC₅₀ = 7.31 μg/mL	^[22][23]		Alanine
Annona squamosa seeds (Ahmedabad, India)		0.594
		Antioxidant	Hexane, acetone, chloroform: methanol (2:1), ethanol (50%) and water seed extract	DPPH assay			Highest antioxidant activity was observed in water (777.64 g GAE/g), while lowest was observed in hexane (268.75 g GAE/g) seed extract	^[57][69]		Methionine + Cystine
Annona squamosa seeds (Alexandria, Egypt)		0.106
	Antioxidant	-	DPPH assay	IC₅₀ value equal to 7.88 µg/mL	^[22][23]	Histidine
Annona squamosa seeds (Ceara, Brazil)	0.139
	Antioxidant	Methanolic seed extract	Fe³⁺ reduction, DPPH and ABTS assay	IC₅₀ value of 0.57, 0.36, and 0.14 mg/mL for Fe³⁺ reduction, DPPH and ABTS assay performed on methanolic seed extract, respectively	^[28][29]	Arginine
Annona squamosa seeds (Southeastern Brazil)	0.704
	Antioxidant	Ethanolic seed extract	DPPH assay	EC₅₀ value of seed extract is 63.19 µg/mL	^[58][70]	Glycine	0.392
Annona squamosa seeds (Lucknow, India)	Antioxidant	Ethanolic seed extract	Alcohol-induced liver damage in Sprague Dawley rats (150–210 g) (dose: 200 and 400 mg/kg po)	Significant elevation in the level of SOD, GSH and CAT and decrease in the level of TBARS	^[31][32]	Valine
Annona squamosa seeds (Lucknow, India)	0.642
	Hepatoprotective	Ethanolic seed extract	Alcohol-induced liver injury in Sprague Dawley rats (150–210 g) (dose: 200 and 400 mg/kg po)	Reduction in ALT, ALP, AST, LDH and SBL and cholesterol level and increase in the level of albumin (p < 0.01–p < 0.001) and total protein (p < 0.05–p < 0.001)	^[31][32]	Threonine
Annona squamosa seeds (Bangalore, India)	0.324
	Hepatoprotective	Hydroalcoholic seed extract	CCl₄-induced hepatotoxicity in rats	Reduction in the level of SGOT (51.22–87.37 U/L), SGPT (38.21–96.22 U/L), ALP (98.28–159.25 U/L) and total bilirubin (0.71–1.47 mg/dL)	^[59][20]	Lysine
Annona squamosa seeds (Mumbai, India)	0.407
	Antipsoriatic/antiproliferative	Seed oil	HaCaT cell line in Oxazolone-induced psoriasis in female Balb/C	Inhibition of growth of HaCaT cells	[19]	Annona squamosa seeds	Polysaccharides	Rhamnose, Fucose, Mannose, Fructose, Arabinose, Galactose, Fructosamine, Galactosamine, Xylose, Glucose, Glucosamine, and Mannuronic, Alluronic, Glucuronic and Galacturonic acid	USP = 0.67–1.27%; FSP = 2.82–3.72%	^[26
Annona squamosa seeds (Madhya Pradesh, India)	^]	[	Antithyroidal	27]
	Methanolic seed extract (dose: 200 mg/kg)		L-T4 (0.5 mg/kg/day) caused hyperthyroid in rats	After treating T4-induced hyperthyroid mice with seed extract (200 mg/kg) for 10 days, the effects of L-T4 were reversed, demonstrating the potential of custard apple seed in controlling hyperthyroidism	^[60][83]	Annona squamosa seeds	Carbohydrates (g/100 g DW (%))
Annona squamosa seeds	Vasorelaxant	-	66.64	^[22][23]
	Cyclosquamosin B		Rat animal model		Inhibitory effect on Ca²⁺ channel, at concentration of 10⁻⁵ M		^[61][77]	Fat (g/100 g DW (%))
Annona squamosa seeds	-	Antiheadlice 29.21
	Petroleum ether seed extract		In vitro		Petroleum ether extract along with coconut oil (1:1), kills 90% of lice		^[62][78]	Fiber (g/100 g DW (%))
Annona squamosa seeds (Pak Chong, Thailand)	-	32.64
Antiheadlice		Hexane seed extract	In vitro against headlice		Seed extract contains oleic acid and a triglyceride with one oleate ester that kills lice in 11–49 min		^[63][84]	Ash (g/100 g DW (%))
Annona squamosa seeds	-		Antihelminthic 1.90
	-		-		Seed extract exhibit antihelminthic activity against Pheritima posthuman and Haemonchus contortus		^[64][79]	Protein (g/100 g DW (%))
Annona squamosa seeds (Fortaleza, Brazil)	-	2.25
	Antihelminthic	Ethyl acetate seed extract	Haemonchus contortus		C37 trihydroxy adjacent bis- tetrahydrofuran acetogenin repressed egg hatching of H. contortus at 25 mg mL⁻¹		^[65][85]	Moisture (g/100 g DW (%))
Annona squamosa seeds	-		Antilarval 3.92
Minerals (mg/kg)	K	56.47–355.84
		^[	⁶⁷		^]		[	86]	Ca	46.90–187.12
		^[	⁶⁷		^]		[	86]	P	33.30–32.75
	Mg	16.22–20.36
	Fe	6.74–20.84
	Cu	0.30–23.91
	Na	9.29–28.27
	Zn	0.43–22.17
	Mn	0.25
Annona squamosa seeds	Crude protein (%)	18.34		^[27][28]
	Crude fiber (%)	17.56
	Crude oil (%)	30.41
	Total carbohydrates (%)	21.80
	Moisture (%)	6.65
	Ash (%)	5.24
Annona squamosa seeds	Moisture (%)	6.7		^[21][22]
	Fat (%)	26.8
	Protein (%)	17.5
	Ash (%)	2.2
	Fiber (%)	16.8
	Tocopherol (mg/100 g)	15.5–16.6
Annona squamosa seeds	Carotenoids (μg of β-Carotene/100 mg)	0.45		^[28][29]
Annona squamosa seeds	Vitamin C (mg AA/100 g)	0.57		^[28][29]

DW—dry weight; FSP—fermented seed polysaccharide; USP—unfermented seed polysaccharide.

3. Phytochemical Profile of Custard Apple Seeds

Phytochemical investigations reported cyclopeptides and annonaceous acetogenins as the chief constituents in the seeds of A. squamosa ^[9][22][9,23]. Different parts of A. squamosa contain several phytochemicals involving alkaloids, such as aporphine, norcorydine, roemerine, corydine, glaucine, anonaine and norisocorydine, in different parts of the plant ^[29][30][30,31]. The seeds of A. squamosa were found to contain acetogenins (polyketide), namely annotemoyin−1 and 2, cholesteryl, coumarinoligans, glucopyranoside, squamocin, and squamocins B-N ^[31][32]. It was demonstrated that the custard apple seeds are toxic, but they are used as a biopesticide or an insecticide (its preparation may cause eye irritation that results in damage to the cornea). Custard apple seeds contain a high oil content and can be used for the production of soap and/or, if treated, can be used as an alternative to cooking oil ^[32][33]. Seeds contain volatile substances such as 12,15-cis-squamostatin-A, bullatacin, β-caryophyllene, α-pinene, β-pinene, anonaine, camphene, spathulenol, germacrene, squamocin, duvariamicin-III, myrcene, liriodenine, annonacin and molvizarin ^[33][34]. In a study, the identification of phytochemicals present in the seed extract of A. squamosa was carried out via Fourier-transform infrared (FTIR) analysis ^[34][35]. The result of the investigation shows the presence of alkenes, imine, oxime, quinone or conjugated ketone, nitro compounds, amides, nitroso compounds, sulfone, aromatics, sulphate ester, alkyl halides, phosphine, ethers, phosphonate, trimethylsilyl, amine oxide, phosphor amide, carboxylic acids, thiocarbonyl esters, phosphine oxide, phosphate, organosilicon, phosphite esters and amines in the methanolic seed extract of A. squamosa. The atmospheric pressure chemical ionization mass spectrometry (APCI-LC-MS) analysis revealed the presence of numerous acetogenins such as squamocin, annonacin and annonacin VI and cyclopeptides such as cyclosquamosin A and B and cyclosquamosin H in the seed extract of A. squamosa ^[34][35]. The earlier studies reported the medicinal properties of squamocin and annonacin present in the seeds of A. squamosa, suggesting that these compounds play a major role in the insecticidal, anti-inflammatory and anticancer properties ^{[33][35][36][37]}[34,36,37,38]. In a study, the seed extract of A. squamosa in different solvent systems (petroleum ether, water and methanol) was tested for phytochemical screening. The presence of alkaloids, carbohydrates, flavonoids, glycosides, phenols, proteins, saponins, sterols, tannins and terpenoids was observed in the methanolic and aqueous seed extract, whereas the presence of only alkaloids, flavonoids and tannins was observed in the petroleum ether extract ^[38][39]. The effects of the extraction conditions and the solvent nature on the total flavonoid content (TFC) and the total polyphenol content (TPC) have been demonstrated in different studies. Nguyen et al., ^[39][40] determined the TPC and TFC from A. squamosa seed extract under different reaction conditions and, from the results, the values of TFC and TPC were observed to be 189.15 mg quercetin equivalent (QE)/100 g DW and 234.17 mg gallic acid equivalent (GAE)/100 g DW, respectively, in the ethanolic seed extract, which are found to be higher in comparison with the methanolic seed extract (183.90 mg QE/100 g DW and 232.01 mg GAE/100 g DW) and the water seed extract (84.90 mg QE/100 g DW and 113.89 mg GAE/100 g DW). A study by Leite et al., ^[28][29], has also determined the TPC and TFC in the methanolic seed extract of A. squamosa and, interestingly, the results showed that the seeds have a significantly higher flavonoid content (893.30 μg QE/g extract), and phenolic content (32.53 μg GAE/mg extract). Flavonoids such as isoquercetin, rutin, quercetin and gallic acid have been identified in the seeds ^[40][41]. The presence of leucoanthocyanins, polyphenols, tannins, triterpenes and unsaturated sterols have also been demonstrated in chemical studies of the A. squamosa seeds ^[41][42]. The seeds of A. squamosa also show the presence of annoglaxin, annosquacin A–D, annosquamin A–C, bullatencin, dotistenin, murisolin, cyclosquamosin B–I, squamin A and B, uvariamicin I–III and many other annonaceous acetogenins and cyclopeptides as the main constituents, each responsible for different functions such as vasorelaxant, cytotoxic against various cancer cell lines, antibacterial and nematicidal, etc. [9]. In a recent study of A. squamosa, phenolic compounds were determined in the seed extract and the result revealed the presence of cinnamic acid and its derivatives involving ferulic acid (5.08 mg/100 g), o-coumaric acid (49.02 mg/100 g) and p-coumaric acid (1.96 mg/100 g), gallic acid, p-hydroxybenzoic acid, salicylic acid and syringic acid in the seeds of A. squamosa. The seeds of the custard apple also show the presence of flavonoids, phenolic compounds, sulfated polysaccharides, tannins and triterpenoids ^[22][23]. In a study conducted by Janicke et al., ^[42][43], it was observed that dietary fiber abundant in ferulic acid, hydroxycinnamic acid and p-coumaric acid are protective against cancer. Furthermore, p-coumaric acid and o-coumaric are reported to be responsible for antimutagenic, anti-inflammatory, antioxidant, antitumor and anticancer activity ^[42][43][43,44]. Recently, fruits of A. squamosa have attracted a lot of attention due to their numerous health benefits. The major nutritional and phytochemical components of A. squamosa seeds are shown in Figure 2 and Figure 3.

Figure 2.

Major nutritional and phytochemical components of

Annona squamosa

seed.

Figure 3.

Structure of important compounds found in seeds of

A. squamosa

4. Pharmacological Properties

Recently, custard apple seeds have emerged as a potential ingredient for the development of supplementary foods because of its significant nutraceutical and phytochemical composition. However, the development of by-products by integrating the bioactive compounds from the custard apple seeds are well-endowed with novel pharmacological properties. These properties of A. squamosa or the custard apple seed have been extensively studied for the antimicrobial, antidiabetic, anti-inflammatory, anticancer, antitumor, antioxidant, hepatoprotective, antiproliferative, antiheadlice, antihelminthic and antilarval activities (Figure 4).

Figure 4.

Biological properties of

Annona squamosa

seeds.

All the biological activities of A. squamosa seeds are mentioned in Table 2 and Figure 4.

Table 2. Pharmacological properties of Annona squamosa seeds.

Variety/Region	Activity	Extract/Solvent Used/Concentration	Study/Cell Line/Animal Model	Key Finding
Annona squamosa seeds (Thiruvananthapuram, Kerala state)

Crude ethanolic seed extract


-


Inhibit larval growth (20-fold) in
Spodptera litura


^[
⁶⁶
^]
[
80
]


Annona squamosa
seeds (Thrissur, Kerala, India)


Larvicidal activity
		Silver nanoparticles (AgNPs) of aqueous seed extract	III and IV instars of Anopheles stephensi	At 60 μg/mL, 100% mortality at III instar is observed. LC₅₀ = 22.44 μg/mL; LC₉₀ = 40.65 μg/mL at III instar stage. At IV instar LC₅₀ = 27.83 μg/mL; LC₉₀ = 48.92 μg/mL
Annona squamosa seeds (Thrissur, Kerala, India)	Antibacterial	Silver nanoparticles (AgNPs) of aqueous seed extract	Staphylococcus aureus, Klebsiella pnuemoniae	Antibacterial activity of AgNPs was found to be efficient compared with plant extract and commercial antibiotic tetracycline

ZOI—zone of inhibition; PEE—petroleum ether extract; ME—methanolic extract; CE—chloroform extract; LPS—lipopolysaccharide stimulated; DPPH—2,2-diphenyl-1-picrylhydrazyl; ABTS—2,2-azinobis (3-ethylbenzothiazoline-6-sulfonic acid) (ABTS).