Annona Squamosa: Benefits, Uses, and Side Effects

Annona squamosa, widely known as sugar apple or custard apple, is a tropical fruit tree whose leaves, seeds, and flesh have been studied for a range of biological activities, from blood-sugar regulation and antioxidant effects to antimicrobial and anticancer properties. The plant belongs to the Annonaceae family and is cultivated across the West Indies, South and Central America, India, Mexico, Egypt, and other warm-climate regions.¹ But the story is not all upside. The same plant that shows promise in laboratory studies also carries real safety risks, particularly from compounds in its seeds and fruit that have been linked to eye damage and neurodegenerative disease.

What the Research Says About Blood Sugar

Among the most-studied benefits of Annona squamosa is its potential to help manage blood sugar. Traditional medicine systems in India and Central America have long used the leaves for this purpose, and modern lab work has started to explain why.² An ethanol extract of the leaves boosted insulin secretion from insulin-producing cells in a dose-dependent way, meaning higher concentrations triggered more insulin release. The mechanism involved changes in the cell membrane that allowed calcium to flow in, a key step in how beta cells in the pancreas normally release insulin. The same extract also slowed down sugar absorption in the gut, improved glucose tolerance, and raised levels of a gut hormone called GLP-1 in rats fed a high-fat diet.³

An earlier animal study using a water-based leaf extract in rats with chemically induced type 2 diabetes also supported these antidiabetic claims.⁴ Together, the evidence from cell studies and rodent experiments is encouraging, but there is an important caveat: no controlled clinical trials in humans have been published. The gap between “it works in a petri dish and in rats” and “it safely helps people” is enormous in pharmacology, so treating custard apple leaves as a proven diabetes remedy would be premature.

Antioxidant Capacity Across Plant Parts

Oxidative stress contributes to aging, cardiovascular disease, and many other chronic conditions, which is why antioxidant-rich foods and plant extracts attract so much research interest. Annona squamosa performs well in laboratory antioxidant assays. Seed extracts tested across multiple methods showed strong free-radical scavenging, with the methanol extract performing best in several tests.⁵ The peel is also a standout. A study of ten sugar apple cultivars grown in Thailand found that the cultivar known as “Fai Keaw” had the highest total phenolic content and the best antioxidant capacity across most assays, suggesting that the peel, which people typically throw away, could serve as a source of natural antioxidants for food products.⁶

An analysis of sugar apple seeds found them to be a meaningful source of lipids, proteins, and carbohydrates. The oil extracted from the seeds was rich in unsaturated fatty acids, particularly oleic and linoleic acids, and contained significant amounts of tocopherols (forms of vitamin E), which are themselves antioxidants.⁷ Keep in mind, though, that high antioxidant performance in a test tube does not automatically translate into health benefits when you eat the fruit. The body processes, absorbs, and metabolizes these compounds in complex ways.

Antimicrobial and Anticancer Findings

A 2024 narrative review catalogued the main biological activities reported for Annona squamosa across the scientific literature, listing cytotoxic, antidiabetic, antimicrobial, antiparasitic, antioxidant, antimalarial, and insecticidal effects.⁸ On the antimicrobial front, peel and seed extracts have shown activity against several bacterial strains in the lab, outperforming the fruit pulp in most cases. One study found that the peel extract was particularly effective against certain Gram-negative bacteria, likely because the peel and seeds concentrate higher levels of active polyphenol compounds than the soft inner flesh.⁹

Cancer research on Annona squamosa has mostly stayed at the cell-culture stage. Organic and water-based seed extracts triggered apoptosis (programmed cell death) in breast cancer and leukemia cell lines by ramping up reactive oxygen species and depleting the cells’ internal defenses. The extracts also suppressed a protein called Bcl-2 that normally helps cancer cells survive.¹⁰ These findings are interesting as leads for drug development, but killing cancer cells in a dish is not the same as treating cancer in a living person. No human trials of custard apple extracts for cancer treatment have been reported.

Traditional and Practical Uses

Long before any laboratory tested its extracts, Annona squamosa had a role in folk medicine across its native and adopted ranges. In India, the leaves have been used to manage high blood pressure and blood sugar, while crushed seeds have served as an insecticide and treatment for parasites.² In parts of Latin America, the fruit has been used to combat intestinal worms, and the bark has been brewed into a tea for diarrhea.

One of the more unusual applications is against headlice. A study prepared a cream from the petroleum ether extract of Annona squamosa seeds and applied it to infested hair for three hours. The result was a kill rate above 95%, higher than what a standard 25% benzyl benzoate emulsion achieved. The cream formulation remained stable for at least 12 months, making it a practical candidate for an alternative headlice treatment.¹¹ While the study was small and has not led to a widely marketed product, it highlights that the insecticidal compounds in the seeds have genuine potency.

The Neurotoxicity Problem

Here is where the story takes a sharp turn. The Annonaceae family, which includes custard apple, soursop, and cherimoya, produces a class of compounds called annonaceous acetogenins. These are potent inhibitors of mitochondrial function in cells, which is partly why they kill cancer cells and parasites in lab studies. But the same mechanism can damage nerve cells, particularly the dopamine-producing neurons that degenerate in Parkinson’s disease.

Researchers have identified squamocin, a specific acetogenin, in the fruit of Annona squamosa and flagged it as an environmental neurotoxin. One study concluded outright that the fruit “should be considered a risk factor for neurodegenerative disorders.”¹² This is not merely theoretical. Research into populations that regularly consume Annonaceae fruits has found associations between consumption and atypical parkinsonism, a group of neurodegenerative conditions that share features with Parkinson’s disease but often progress faster and respond less well to standard medication. In vitro and in vivo studies confirm that acetogenins damage not only the dopamine system but also other populations of brain cells, contributing to cognitive deficits alongside motor symptoms.¹³

The risk appears to depend on how much and how often someone eats these fruits. Occasional consumption by a healthy person is unlikely to cause immediate neurological harm, but long-term, heavy consumption, particularly of the seeds (where acetogenin concentrations tend to be highest), raises genuine concern. If you have a family history of Parkinson’s disease or already show early motor symptoms, this is worth discussing with a doctor rather than dismissing.

Eye Toxicity from Seed Exposure

A very different hazard comes from direct contact between custard apple seeds and the eyes. A clinical case series documented six consecutive patients who developed toxic keratoconjunctivitis, a painful inflammation of the cornea and surrounding eye tissue, within 6 to 12 hours of accidental ocular exposure to the seeds.¹⁴ This is not an allergic reaction limited to sensitive individuals; the compounds in the seed coat are chemically irritating.

In practice, this means you should wash your hands after handling custard apple seeds and avoid touching your eyes. If you are using the seeds to make a paste for insecticidal purposes, such as the headlice cream mentioned earlier, wear gloves and keep the preparation away from your face. Parents should be aware that children playing with the seeds can inadvertently transfer the irritant to their eyes.

Potential Drug Interactions

Because Annona squamosa extracts can lower blood sugar through multiple mechanisms, there is a real chance of interaction with conventional diabetes medications. One animal study explored this directly, combining Annona squamosa extract with glipizide, a commonly prescribed sulfonylurea drug. In diabetic rats, the combination controlled blood glucose better than either the herbal extract or the drug alone. The researchers suggested that combining the two could allow a reduction of the glipizide dose by as much as half.¹⁵

That may sound appealing, but it is also a warning. If you are taking oral diabetes drugs and start consuming large amounts of custard apple leaf tea or a concentrated supplement, the combined blood-sugar-lowering effect could push your glucose dangerously low. Hypoglycemia can cause dizziness, confusion, fainting, and in severe cases, seizures. This is not a reason to avoid eating the fruit in normal quantities, but if you are managing diabetes with medication, do not self-prescribe concentrated extracts without medical guidance.

Growing Conditions and Plant Characteristics

Sugar apple is a small, semi-deciduous tree that thrives in warm climates. Research on seedling growth confirms that it favors warmer temperatures, with shoot length and leaf production both greater under warm conditions compared to cool ones.¹⁶ This heat preference explains why the tree does well in equatorial and subtropical zones but struggles in regions where temperatures regularly drop below about 10°C. It is generally more sensitive to cold than its close relative the cherimoya.

The fruit itself is roughly fist-sized with a bumpy, segmented green skin that turns slightly yellowish as it ripens. Inside, the white pulp separates easily into custard-like segments, each containing a hard, glossy black seed. The sweetness of ripe sugar apple pulp is intense and distinctive, with flavor notes that people often compare to a blend of banana and pineapple with a creamy texture. Trees grown from seed typically fruit within three to four years, and hand pollination is sometimes used commercially because the flowers do not self-pollinate efficiently.

Who Should Be Cautious

The fruit pulp in moderate quantities is widely eaten across the tropics without obvious harm. The concerns stack up when you move beyond casual consumption or start handling plant parts that concentrate bioactive compounds. The groups that warrant extra care include:

People on diabetes medication: concentrated leaf preparations could amplify blood-sugar-lowering effects and cause hypoglycemia.
Pregnant and breastfeeding women: there is essentially no safety data on concentrated Annona squamosa extracts in pregnancy, and some of the cytotoxic and insecticidal compounds in the seeds are potent enough to raise concern.
Anyone with a personal or family history of Parkinson’s disease or parkinsonism: the acetogenins present in the fruit, and especially the seeds, are linked to neurodegeneration.
Children: accidental exposure of seed material to the eyes can cause painful inflammation, and children are more likely to rub their eyes with contaminated hands.

These cautions apply mainly to concentrated preparations, seeds, and heavy long-term consumption. Eating a ripe sugar apple from time to time is not the same as drinking a daily tea made from crushed seeds.

What the Seeds Contain Beyond Toxins

Given all the warnings about seeds, it is worth noting that they are chemically complex and not purely hazardous. The oil extracted from sugar apple seeds has been characterized as a good source of unsaturated fatty acids, especially oleic acid (the same kind found in olive oil) and linoleic acid (an essential fatty acid the body cannot make on its own). The seeds also contain notable amounts of tocopherols.⁷ This nutritional profile has led some researchers to suggest the seeds could be useful in food and animal feed, but any such application would need to address the acetogenin content, either through selective breeding of low-acetogenin cultivars or processing methods that remove or deactivate the neurotoxic compounds.

This dual nature of the seed, nutritious oil on one hand and potent toxins on the other, is a recurring theme in Annonaceae research. It also illustrates why blanket statements like “natural is safe” fall apart under scrutiny. A single seed contains compounds that fight cancer cells, kill lice, nourish with healthy fats, damage eyes on contact, and may harm the brain over time. Whether a compound is beneficial or dangerous depends entirely on the dose, the route of exposure, and the person involved.

Sugar Apple Versus Soursop

People sometimes confuse Annona squamosa with its close relative Annona muricata (soursop or graviola), which has received even more media attention for its purported anticancer properties. The two species share many of the same compound classes, including acetogenins, polyphenols, and flavonoids, but they differ in fruit size, taste, and the concentrations of specific chemicals. Soursop fruit is larger and more acidic, while sugar apple is smaller and sweeter. Both carry the same general neurotoxicity concern from acetogenins, and neither has been validated in human clinical trials for cancer treatment despite decades of cell-culture and animal research.

From a nutritional standpoint, both seeds are good sources of lipids and unsaturated fatty acids, and both exhibit strong antioxidant activity from their phenolic compounds.⁷ If you see health-supplement marketing that promotes one species while ignoring the neurotoxicity data, apply the same skepticism regardless of whether the product is labeled custard apple, sugar apple, soursop, or graviola. The acetogenin risk runs through the entire family.