8.0 Antioxidant Activity

Studies report widely differing levels of anti-oxidants in Annona spp.  Studies conducted in India (Kaur and Kapoor, 2005), Taiwan (Chen, et al. 2006), and Costa Rica (Franco, 2006) show that Annona squamosa, Annona cherimola and Annona muricata have high anti-oxidant activity.  In contrast, a DPI&F study (Treloar, 2006; unpublished data) showed that Annona spp. hybrids have very low levels of antioxidants.  These discrepancies may be due to varietal differences, method of analyses or time of sampling.  

In the Taiwanese study (Chen, et al. 2006), the antioxidant activity in mature fruits of 36 species and varieties produced in Taiwan was analysed by the ferric reducing antioxidant power (FRAP) assay.  In this study, sugar apple was categorised as having very high antioxidant activity >70mmol/100g edible part.

9.0 Effects On Cardio-Vascular Disease

Hole et al. (2006) studied the effects of fruit pulp of Annona reticulata L. fruits (ARF) on heart disease in rats.  They selected the aqueous extract of dried fruits of Annona reticulata (ARF) because it was found to possess significant in vitro antioxidant potential in preliminary screening.  Hole et al. (2006) tested the protective effect of aqueous extract of the fruits on isoproterenol induced myocardial infarction (death of heart tissue) in rats.  ARF was administered orally in two different doses (100mg/kg, 200mg/kg) for 21 days.  Histopathological observations of the heart tissue of rats challenged with isoproterenol showed confluent necrosis (death), separation of muscle fibers and inflammatory infiltrations. ARF pre-treatment protected these morphological changes, thus supporting evidence for the cardioprotective activity of ARF (Figure 1).

Hole et al. (2006) concluded from their studies that  chronic oral administration of ARF 100 and 200 mg/kg prevented isproterenol-induced alterations in lipid profile, marker enzyme activity, endogenous antioxidant levels and cellular damage wherein the results are comparable with captopril (a drug used to treat heart failure), which was used as a positive control in the study.  

Assuming that bioavailability in rats is similar to humans, for an 80 kg human, this would be equivalent to eating 80 g (or about 16 g dried) of fresh pulp (about a quarter segment of normal size custard apple fruit) per day.

Figure 1.
Plate 1: Photomicrographs of heart section from rat from normal group.	Plate 2: negative control group treated with a chemical to induce death of heart tissue.
Plate 3: Annona reticulata pulp 100 mg/kg.	Plate 4: Annona reticulata pulp 200 mg/kg.
Plates 3 and 4 show the protective effect of Annona reticulata pulp as tissues more closely resemble the control group in Plate 1.