Annona is a genus of roughly 170 species of tropical and subtropical fruit trees in the family Annonaceae, and it includes some of the most prized edible fruits in warm-climate agriculture: cherimoya, soursop, sugar apple, and their hybrid atemoya. These fruits share a distinctive creamy, aromatic flesh that Mark Twain reportedly called “the most delicious fruit known to men” (referring to cherimoya), yet they remain relatively obscure outside the tropics. Beneath their custard-like appeal lies a surprisingly complex biology, from flowers that heat themselves to attract beetle pollinators to potent chemical compounds that have drawn attention from both cancer researchers and neurologists.
The Major Species and How They Differ
When people say “annona,” they usually mean one of four commercially relevant species. Cherimoya (Annona cherimola) grows best at cooler tropical elevations, roughly 1,000 to 2,000 meters, and thrives in parts of Peru, Ecuador, Spain, and California. Its heart-shaped green fruit has smooth or slightly bumpy skin and a complex flavor often compared to a blend of banana, pineapple, and strawberry. Soursop (Annona muricata) is a lowland tropical species with large, spiny green fruit that can weigh several kilograms. Its tangy, more acidic pulp makes it popular for juices, smoothies, and ice cream across the Caribbean, Southeast Asia, and West Africa. Soursop has also been used widely as a traditional medicine for ailments ranging from fever to parasitic infections.1PubMed Central. Pharmacological Activities of Soursop (Annona muricata Lin.)
Sugar apple (Annona squamosa), sometimes called custard apple or sweetsop, is the most widely cultivated Annona species in the tropics. Its knobby, segmented skin breaks apart easily when ripe, revealing intensely sweet white flesh. It is a staple fruit in India, Thailand, and parts of Central America. Then there is atemoya, a hybrid of cherimoya and sugar apple (A. cherimola × A. squamosa), deliberately bred to combine cherimoya’s flavor complexity with sugar apple’s heat tolerance. Australian production is dominated by atemoya cultivars like ‘African Pride’ and ‘Pinks Mammoth.’2Acta Horticulturae. BREEDING NEW VARIETIES OF ATEMOYA (ANNONA SPP. HYBRIDS)
Beyond these four, other species see regional cultivation. Ilama (A. diversifolia) is eaten in parts of Mexico and Central America, and bullock’s heart (A. reticulata) appears in traditional orchards across South Asia. These less common species also serve as parents in breeding programs aimed at producing improved hybrids.3Acta Horticulturae. BREEDING NEW VARIETIES OF ATEMOYA (ANNONA SPP. HYBRIDS)
Where Annona Actually Comes From
For decades, the assumption was that cherimoya originated in the Andes, partly because Peru and Ecuador harbor enormous diversity of the species. More recent genetic and biogeographical analysis has challenged that story. Phylogenetic work using molecular markers now supports a Mesoamerican origin for A. cherimola, suggesting the species dispersed southward into South America rather than the other way around.4Journal of Systematics and Evolution. Phylogenetics of Annona cherimola (Annonaceae) and some of its closest relatives This matters for conservation and breeding, because it shifts the expected location of the species’ deepest genetic diversity. Meanwhile, soursop and sugar apple are generally accepted as originating in the lowland Neotropics, spreading through human cultivation to Africa and Asia centuries ago.
Beetle Pollination and the Problem It Creates for Farmers
Annona flowers have an unusual reproductive quirk that shapes everything about how these trees are farmed. The flowers are protogynous, meaning the female parts mature before the male parts. A flower opens in its female stage, receptive to pollen, but its own pollen is not yet available. By the time the stamens release pollen, the stigma has already passed receptivity. This makes self-pollination within a single flower almost impossible and means the plant depends entirely on something carrying pollen from an older flower to a younger one.
In the wild, that something is beetles. Dynastid scarab beetles are the main or exclusive pollinators of Annona species with large flowers. They are nocturnal, drawn to the flowers by strong, fruity odors generated partly by a remarkable feat of thermogenesis: the flowers can heat themselves as much as 10 to 15 degrees Celsius above ambient air temperature.5Plant Systematics and Evolution. Beetle pollination and flowering rhythm of Annona spp. (Annonaceae) in Brazil This heat volatilizes the scent compounds and may also provide a warm refuge for the insects. Beetles crawl into the floral chamber, feed on nutritious tissue at the base of the petals, and in the process deposit pollen they picked up from a previously visited flower. When the stamens eventually open and shed pollen inside the still-closed chamber, the beetles get dusted again and carry it onward. In Brazilian cerrado, Cyclocephala beetles have been identified as the primary pollinators of A. coriacea, with a second beetle genus, Arriguttia, also contributing.6PubMed Central. Beetle pollination and flowering rhythm of Annona coriacea Mart. (Annonaceae) in Brazilian cerrado: Behavioral features of its principal pollinators
Sugar apple flowers likewise show classic beetle-pollination traits: pendulous orientation, restricted petal movement that excludes larger visitors, and floral thermogenesis.7Scientia Horticulturae. Pollination biology of Annona squamosa L. (Annonaceae): Evidence for pollination syndrome The trouble is that the specialized beetle pollinators often do not exist, or exist in low numbers, in regions where Annona is grown commercially. Without enough beetles, fruit set from natural pollination is generally too low to produce commercially acceptable yields.8Scientia Horticulturae. Effects of storage length and flowering stage of pollen influence its viability, fruit set and fruit quality in ‘Red’ and ‘Lessard Thai’ sugar apple and ‘Gefner’ atemoya This is the central bottleneck of Annona farming.
Hand Pollination and Breeding Goals
Because natural pollination so often fails in orchards, commercial Annona growers around the world resort to hand pollination. The process is labor-intensive: workers collect pollen from flowers in the male stage, typically in late afternoon, and brush or squirt it onto flowers that have just opened into the female stage. Timing matters enormously. Hand pollination performed in the evening, right after pollen collection, produces better results than storing pollen overnight, suggesting that pollen viability declines faster than stigma receptivity.9Scientia Horticulturae. Hand pollination effects on the set and development of cherimoya fruit in a humid climate When done well, hand pollination pushes fruit set above 80 percent, and in cherimoya, self-pollinated flowers produced more symmetrical, heavier fruit than cross-pollinated ones.10Scientia Horticulturae. Hand pollination effects on the set and development of cherimoya fruit in a humid climate
The expense of hand pollination is one of the main reasons Annona fruits remain costly. In Australia, breeding programs for atemoya have explicitly targeted higher self-pollination rates as a key goal, alongside smoother skin, symmetrical shape, and low seed counts. The Australian program set a benchmark of fewer than 10 seeds per 100 grams of pulp, along with reduced blemish susceptibility.11Acta Horticulturae. BREEDING STRATEGIES FOR ATEMOYA AND CHERIMOYA Breeders have also made interspecific crosses involving four different species to widen the genetic base and introduce traits like disease resistance or improved texture.12Acta Horticulturae. BREEDING NEW VARIETIES OF ATEMOYA (ANNONA SPP. HYBRIDS)
How the Fruit Ripens and Why It Is So Perishable
Annona fruits are climacteric, meaning they undergo a burst of respiration and ethylene production after harvest that drives rapid softening and flavor development. Soursop shows a dramatic biphasic respiratory pattern: carbon dioxide production spikes once, dips, and then spikes much higher, reaching roughly 350 milliliters per kilogram per hour at room temperature. Ethylene peaks between these two respiratory surges.13Scientia Horticulturae. Growth, maturation and ripening of soursop (Annona muricata L.) fruit Cherimoya follows a similar double-sigmoid respiration curve, though the timing varies between cultivars.14Postharvest Biology and Technology. Development of flavor-related metabolites in cherimoya fruit and their relationship with ripening physiology
This aggressive ripening metabolism is why Annona fruits have such a short shelf life. A ripe cherimoya or soursop goes from perfect to brown and fermented in a day or two at room temperature. Cold storage slows things down but introduces its own problems: chilling injury can damage the skin and alter flavor if temperatures drop too low. The narrow handling window is a major reason these fruits rarely appear in supermarkets outside the tropics, and why much of the soursop trade relies on frozen pulp rather than whole fruit.
Nutritional Value
Annona fruits are good sources of vitamin C, dietary fiber, and B vitamins, with modest amounts of minerals like potassium and magnesium. Cherimoya, for instance, contains lutein as its most abundant carotenoid, with levels ranging from about 129 to 232 micrograms per 100 grams depending on cultivar, and the peel carries substantially more antioxidant capacity and flavonoids than the flesh.15PubMed Central. Nutritional and phytochemical composition of Annona cherimola Mill. fruits and by-products: Potential health benefits The calorie content is moderate, mostly from natural sugars, making these fruits energy-dense compared to watery tropical fruits like papaya or watermelon.
Acetogenins and the Neurotoxicity Concern
Annona species produce a distinctive class of chemical compounds called annonaceous acetogenins. These molecules are unusually potent inhibitors of mitochondrial complex I, an essential part of the cellular energy-production chain. Structural studies have shown that acetogenins bind along the full length of the ubiquinone-binding channel in complex I, locking into place through two hydrophilic groups positioned to match specific regions within the otherwise water-repelling channel.16PubMed Central. Cryo-electron microscopy reveals how acetogenins inhibit mitochondrial respiratory complex I This potent inhibition is why acetogenins have attracted interest both as potential anticancer agents and as potential health hazards.
The hazard side of the equation centers on neurotoxicity. Epidemiological observations in the French Caribbean, particularly Guadeloupe, identified high consumption of soursop fruit as a risk factor for an atypical form of parkinsonism. The condition, sometimes called Guadeloupean parkinsonism, involves not just the movement symptoms typical of Parkinson’s disease but also cognitive deficits and features that resemble a different neurodegenerative disorder called progressive supranuclear palsy.17PubMed Central. Annonaceae Consumption Worsens Disease Severity and Cognitive Deficits in Degenerative Parkinsonism The suspected culprit is annonacin, a prototypical acetogenin found in soursop fruit and leaves. In lab settings, annonacin triggers tau pathology in neurons (the same kind of protein abnormality seen in Alzheimer’s disease and related conditions), and it causes neurodegeneration in several animal models.18Studies in Natural Products Chemistry. Bioactive Annonaceous Acetogenins
Pharmacokinetic work in rats has shown that when annonacin is given orally, only about 3 percent of the dose reaches the bloodstream, suggesting fairly low bioavailability from eating fruit.19PubMed. Method development for quantification of the environmental neurotoxin annonacin in Rat plasma by UPLC-MS/MS and application to a pharmacokinetic study But the concern is cumulative exposure over years in populations where soursop is a daily dietary staple or consumed as herbal tea made from the leaves, which contain higher concentrations of acetogenins than the fruit pulp. This is still an area of active investigation, and no regulatory agency has banned soursop consumption. The evidence is strong enough, though, to warrant caution about very heavy, long-term intake, particularly of leaf-based preparations.
Cancer Research and the Soursop Hype
The internet is awash with claims that soursop cures cancer. The reality is more measured. Lab studies have shown that extracts from Annona muricata leaves kill various human cancer cell lines in petri dishes. In breast cancer cells, the extracts triggered cell death by activating caspase enzymes and shifting the balance between pro-death and pro-survival signals inside the cell.20PubMed Central. Antiproliferation Activity and Apoptotic Mechanism of Soursop (Annona muricata L.) Leaves Extract and Fractions on MCF7 Breast Cancer Cells Similar results have been observed in colon cancer cells21PubMed. Annona muricata leaves induce G₁ cell cycle arrest and apoptosis through mitochondria-mediated pathway in human HCT-116 and HT-29 colon cancer cells and lung cancer cells, where the extracts showed selectivity for the cancer line over normal cells.22PubMed Central. Annona muricata leaves induced apoptosis in A549 cells through mitochondrial-mediated pathway and involvement of NF-κB
Killing cancer cells in a dish, however, is not the same as treating cancer in a person. Hundreds of compounds that look promising in cell-culture experiments fail in animal models or clinical trials. No randomized controlled trial has tested soursop or its acetogenins in human cancer patients. And the same mitochondrial-inhibiting mechanism that makes acetogenins toxic to cancer cells is the mechanism linked to neurotoxicity. Pursuing one effect inevitably risks the other. For now, soursop leaf teas and supplements marketed as cancer treatments are running far ahead of the evidence, and the neurotoxicity data suggest that high-dose, long-term use of these products carries real risk.
Antidiabetic Research in Animal Models
Another stream of pharmacological interest concerns blood-sugar regulation. Multiple animal studies have explored Annona species for antidiabetic effects. An ethanolic extract of sugar apple leaves fed to diabetic rats produced a substantial reduction in fasting blood glucose over a 10-day treatment period, and improved cholesterol profiles in diabetic rabbits.23Journal of Ethnopharmacology. Hypoglycemic and antidiabetic effect of ethanolic extract of leaves of Annona squamosa L. in experimental animals A review of soursop research identified several proposed mechanisms, including inhibition of enzymes that break down starch and sugar in the gut, enhanced glucose uptake in peripheral tissues, and stimulation of insulin release.24PubMed Central. Annona muricata: Comprehensive Review on the Ethnomedicinal, Phytochemistry, and Pharmacological Aspects Focusing on Antidiabetic Properties
More recent work has looked at kidney protection in diabetic animals. A phenolic-rich soursop leaf extract improved antioxidant enzyme levels and reduced markers of inflammation and kidney damage in diabetic rats, suggesting a potential role in managing diabetic kidney disease.25Scientific African. Protective effect of phenolic-rich extract of Anona muricata Linn leaf on renal oxidative stress and inflammation in streptozotocin-induced diabetes in diabetic rats These findings are interesting but carry the same caveat as the cancer research: animal and cell studies do not automatically translate to human benefit, and no controlled human clinical trial has confirmed antidiabetic effects from Annona consumption.
Insecticidal Properties
Before modern synthetic pesticides, Annona seeds were already known in traditional agriculture as a natural insecticide. The seeds are rich in acetogenins, alkaloids, and flavonoids, and their toxicity to insects has been verified experimentally. Seed extracts from both soursop and sugar apple showed significant insecticidal effects against Aedes and Culex mosquitoes, the vectors of dengue, Zika, and filariasis. Soursop seed extracts were more lethal than sugar apple across the concentrations tested.26Asian Pacific Journal of Tropical Biomedicine. Efficacy of seed extracts of Annona squamosa and Annona muricata (Annonaceae) for the control of Aedes albopictus and Culex quinquefasciatus (Culicidae) In parts of South and Southeast Asia, ground Annona seeds are still used informally as a lice treatment and grain-storage protectant, a practice with centuries of history.
Drought Tolerance and Stress Memory in Sugar Apple
Sugar apple is often considered one of the tougher Annona species, tolerating drier conditions better than cherimoya or soursop. Research into the mechanism behind this tolerance has revealed some intriguing physiology. When sugar apple trees experience drought, they boost their internal levels of abscisic acid (ABA), a hormone that signals stress, and simultaneously increase ascorbic acid (vitamin C) concentration in both leaves and fruit. The stressed fruit actually ends up with higher antioxidant activity and more sugar at harvest compared to well-watered controls.27Scientia Horticulturae. Changes in abscisic acid and antioxidant activity in sugar apples under drought conditions This has led some growers to experiment with deliberate mild drought stress before harvest to improve fruit quality.28Agriculture and Natural Resources. Pre-harvest drought stress treatment improves antioxidant activity and sugar accumulation of sugar apple at harvest and during storage
Even more striking, sugar apple seedlings appear to “remember” drought. When subjected to repeated cycles of dehydration stress, the seedlings showed measurable changes in hormone profiles during the second round that differed from the first. Concentrations of certain growth and defense hormones accumulated further in the second drought, while chlorophyll levels and free-radical-scavenging activity dropped more sharply, suggesting the plant was shifting resources toward survival at the expense of growth. This stress memory may help wild populations endure unpredictable dry seasons in their native habitat.29Fruits. Dehydration stress memory: Insights from physiological responses of sugar apple (Annona squamosa L.) to repeated dehydration stress
Value Chains and On-Farm Conservation
Annona fruits occupy an unusual economic niche. They are rarely traded as global commodities in the way bananas or mangoes are, mainly because of their fragility and short shelf life. Instead, most Annona commerce is regional. In Peru, the cherimoya value chain splits into at least two distinct tracks: fruit from Lima province gets graded, selected, and exported to neighboring Andean countries, generating substantially more value for both producers and traders, while locally produced cherimoyas from other regions follow a less organized chain with lower returns.30Tropical Conservation Science. Value Chains of Cherimoya (Annona Cherimola Mill.) in a Centre of Diversity and its on-Farm Conservation Implications Spain is the world’s largest cherimoya exporter, concentrating production along the subtropical coast of Granada and Málaga, while Australia and Israel have developed small but growing atemoya export industries.
The economic fragmentation has conservation implications. Many Annona species and landraces persist only in backyard orchards and small farms, maintained by individual growers rather than formal gene banks. When economic pressures push smallholders to switch to higher-return crops, unique local varieties can vanish within a generation. Some species face more acute threats: Annona deceptrix, endemic to the Ecuadorian coast, is classified as vulnerable due to habitat degradation from human activities.31Genetic Resources and Crop Evolution. Genetic diversity and structure populations in Annona deceptrix (Westra) H. Rainer (Annonaceae), an endangered species from Ecuador Genetic studies of its remaining populations are underway to guide conservation priorities, but the broader pattern of neglect is common across tropical fruit tree genera whose diversity has never been systematically catalogued.