176 Papaya
ripe papaya or any food containing papaya, or meat tenderised with papain. People
who eat too much papaya and ingest high levels of papain may develop symptoms
consistent with hay fever or asthma, including wheezing, breathing difficulties and
nasal congestion.
Papaya releases a latex fluid when not quite ripe, which can cause irritation and
provoke allergic reaction in some people. Externally the papaya latex is an irritant to
the skin and internally it causes severe gastritis due to high fibre content of papaya
and also contributes to unrest of the digestive system. The latex of the fruit’s skin
can also cause irritation of the stomach. The latex concentration of unripe papayas
is speculated to cause uterine contractions, which may lead to a miscarriage. Skin
irritation is caused to papaya harvesters because of the action of fresh papaya latex
and possible hazard of consuming undercooked meat tenderised with papain. Papaya
is frequently used as a hair conditioner, but should be used in small amounts (Saran
and Choudhary 2013). Some people are allergic to various parts of the fruit and even
the enzyme papain has its negative properties. Papaya seed extracts in large doses
have a contraceptive effect on rats and monkeys, but in small doses have no effect on
the unborn animals. Excessive consumption can cause carotenemia, the yellowing of
soles and palms, which is otherwise harmless. Papaya contains about 6% of the level
of beta carotene found in carrots, which is the most common cause of carotenemia
(Bamisaye et al. 2013).
16.2.2 antioxidantS and Free radicaL Scavenging activity
Phytochemical analysis of leaf extracts revealed the presence of alkaloids, glycosides,
flavanoids, saponins, tannins, phenols and steroids (Gill 1992; Owoyele et al. 2008).
The stems, leaves and fruits of papaya contain plenty of latex. The latex of papaya
is a rich source of four cysteine endopeptidases namely papain, chymopapain, gly-
cylendopeptidase and caricain—a papaya endopeptidase II (Azarkan et al. 2003). As
the fruit ripens, papain and chymopapain get degraded and are not present in the ripe
fruit (Oloyede 2005). Other components include a mixture of cysteine endopeptidases
such as endopeptidase IV, omega endopeptidase, class-II and class-III chitinase and
an inhibitor of serine protease (Odani et al. 1996; Azarkan et al. 1997; El Moussaoui
et al. 2001). The aqueous extract of unripe C. papaya administered orally in Wistar
albino rats demonstrated no adverse effect on the histology of liver, kidney, heart and
small intestine (Oduola et al. 2010).
The leaves, seeds and juice show free radical scavenging and antioxidants
activity. The antioxidant activity of various fractions (ethanol, petroleum ether,
ethyl acetate, n-butanol and aqueous extract) from seeds was evaluated and showed
that ethyl acetate and n-butanol fractions demonstrated antioxidant and free radi-
cal scavenging activity than other fractions (Zhou et al. 2011). Papaya juice is an
efficient scavenger of highly reactive hydroxyl radicals (Webman et al. 1989), which
significantly decreased the lipid peroxidation levels and increased the antioxidant
activity in rats (Mehdipour et al. 2006). The leaf extract of C. papaya evidenced
significant antioxidant and free radical scavenging potential (Okoko and Ere 2012).
The peroxidase is present in the unripe fruit but it is gradually decreased after fruit
ripening (Pandey et al. 2012). The pulp of papaya is rich in benzyl glucosinolate in