Scientific Name(s): Psidium guajava L.
Common Name(s): Goiabeira, Guava, Guayabo, Guyava, Kuawa, Red guava
Clinical trials are lacking. Very limited evidence exists to support guava's use in treating diarrhea, type 2 diabetes, dysmenorrhea, hyperlipidemia, and hypertension.
Limited clinical trials guide dosage recommendations. Diarrhea: Eight hourly doses of guava extract standardized to 1 mg of quercetin per 500 mg capsule for 3 days. Dysmenorrhea: Daily guava leaf extract standardized to 6 mg flavonoid content/day. Hyperlipidemia and hypertension: 0.4 to 1 kg/day of guava fruit added to the diet for 4 to 12 weeks.
None identified except hypersensitivity.
Information regarding safety and efficacy in pregnancy and lactation is lacking.
None well documented.
No serious adverse reactions have been reported in limited clinical trials.
Data are limited.
- Myrtaceae (myrtle)
P. guajava is a large evergreen shrub or small tree that grows up to 15 m in height. It is native to and widely distributed in Mexico and Central America and is common throughout all warm areas of tropical America and the West Indies. Today, the plant is cultivated from Asia to the west coast of Africa, with varieties originally introduced over the past 300 years from the United States. The guava berry, also known as guava, is an important tropical fruit that is primarily consumed fresh. The berry contains several small seeds and consists of a fleshy pericarp and seed cavity with pulp.1, 2
The young leaves of the plant have been used as a tonic to treat digestive conditions such as dysentery and diarrhea in the indigenous medical systems of Brazil and Mexico. Mexican medicinal data document the treatment of acute diarrhea, flatulence, and gastric pain by using a guava leaf water decoction for oral administration 3 times daily. A decoction of young leaves and shoots has been prescribed as a febrifuge and a spasmolytic. In Bolivia and Egypt, guava leaves have been used to treat cough and pulmonary diseases; they have also been used to treat cough in India and as an anti-inflammatory and hemostatic agent in China.
Guava bark has been used medically as an astringent and to treat diarrhea in children, while the flowers have been used to treat bronchitis and eye sores and to cool the body. The fruit has been used as a tonic and laxative and for treatment of bleeding gums. The plant has been used in Africa and Asia to prevent and treat scurvy and to treat hypertension in western Africa. Ethnomedicinal reports document use of the plant in treating malaria. Scientific investigations of the medicinal properties of guava leaf products date back to the 1940s.
Pakistan, India, Brazil, and Mexico are the major commercial producers of guava fruit. Hawaii is the largest producer in the United States. Processed guava products include beverages, cheese, ice cream, jams, jellies, juice, syrup, toffee, wine, and dehydrated and canned products.2, 3
Phytochemical analyses of guava leaf reveal alkaloids, anthocyanins, carotenoids, essential oils, fatty acids, flavonoids (especially quercetin), lectins, phenols, saponins, tannins, triterpenes, and vitamin C (80 mg per 100 g of guava).3, 4, 5, 6, 7, 8, 9
The essential oil contains alpha pinene, caryophyllene, cineol, D-limonene, eugenol, and myrcene. The major constituents of the volatile acids include (E)-cinnamic acid and (Z)-3-hexenoic acid.5, 10 The guava fruit has a high water content with lesser amounts of carbohydrates, proteins, and fats. The fruit also contains iron, vitamins A and C, thiamine, riboflavin, niacin, and manganese. The characteristic fruit odor is attributed to carbonyl compounds. Unripe fruits are high in tannins. The major constituent of the fruit skin is ascorbic acid, largely destroyed by canning and processing.2
Uses and Pharmacology
Guava leaf extracts decreased spasms associated with induced diarrhea in rodents. Reduced defecation, severity of diarrhea, and intestinal fluid secretion reductions have also been demonstrated.2, 3, 12, 13, 14, 15, 16 Activity is generally associated with the ability of quercetin and its derivatives to affect smooth muscle fibers via calcium antagonism, inhibit intestinal movement, and reduce capillary permeability in the abdominal cavity.12, 16
In vitro studies suggest leaf and bark extracts are bactericidal against a range of pathogens causative of diarrhea2; however, data from controlled clinical trials are limited, and few of the trials have been published in peer-reviewed journals. Trials have evaluated guava leaf extract in infantile viral enteritis,16 infectious gastroenteritis,17 and acute diarrhea2 with improvement in outcome measures including number of daily stools, time to cessation, stool composition, and abdominal pain and spasms for P. guava-treated patients.
In an animal model, a water-alcohol extract of P. guajava depressed guinea pig atrial contractility in a concentration-dependent manner. The negative inotropic effect of the extract was blocked by atropine sulfate. In hypertensive rats, intravenous administration of guava leaf aqueous extracts produced a dose-dependent reduction in systemic arterial blood pressure and heart rate.10, 18 The effect of guava leaf extract on isolated vascular smooth muscle and aortic rings has also been evaluated.19, 20
Hypolipidemic activity has been demonstrated in rats administered raw fruit peel.24
Limited evidence from a few clinical trials suggests that the addition of guava fruit or guava leaf tea to the diet can improve the lipid profile. Trials were conducted over a range of doses (0.4 to 1 kg/day) and duration from 4 to 12 weeks.21, 22, 23, 25
Extracts of guava bark, leaves, and fruit containing tannins, flavonoids, triterpenes, and quercetin have been evaluated in induced-diabetic rats. In some, but not all, experiments, no effect was observed in either normal rats or normal glucose-loaded rats. A polyphenolic effect may be responsible for the observed inhibition of low-density lipoprotein glycation.2, 26, 27, 28 Inhibition of protein tyrosine phosphatase 1B29 as well as increased glucose uptake in rat hepatocytes has also been described.30
Limited evidence from a few clinical trials suggests guava fruit31 and leaf tea extracts may be of benefit in type 2 diabetes.2, 25, 32, 33 Reductions in postprandial serum glucose levels of a lesser size than chlorpropamide and metformin have been demonstrated, and inhibition of alpha-glucosidase enzymes has been suggested to play a role in the mechanism of action.25
An in vitro study using uterine tissue from rats demonstrated a spasmolytic effect of guava leaf extract.34 Activity is postulated to be due to an estrogenic effect of the flavonoids or to anti-inflammatory effects.
Decreases in dysmenorrheal pain intensity were reported after 4 months of daily guava leaf extract standardized at 6 mg of flavonoid content per day.2 A Cochrane systematic review and meta-analysis of dietary supplements for dysmenorrhea identified only low or very low quality studies with very small sample sizes. No consistent evidence of effectiveness was found for the treatment of primary dysmenorrhea with guava compared to placebo or no treatment; however, no difference was identified between guava extract 3 mg and 6 mg compared to ibuprofen 400 mg (1 randomized clinical trial, n = 155).59
Leaf and bark extracts have demonstrated in vitro antimicrobial activity mostly associated with flavonoids, such as morin glycosides, quercetin, and quercetin glycosides.38, 39, 40 Activity has been demonstrated against a wide range of gram-positive and gram-negative human pathogens including Escherichia coli, Vibrio cholera, Giardia lamblia, and Shigella species, as well as Staphylococcus aureus and Pseudomonas aeruginosa.2, 7, 9, 11, 41, 42, 43, 44, 45, 46 Data from in vivo animal or clinical studies are lacking.
Aqueous extracts from P. guajava have antioxidant or radical-scavenging activity. Most of the activity is associated with the polyphenols; however, the guava extracts also contain antioxidants, such as ascorbic acid and carotenoids.47, 48, 49
Leaf extracts, leaf oil, guava seed, and whole plant extracts have been evaluated for potential chemotherapeutic applications. Activity against various human cancer cell lines have been demonstrated including prostate, colon, and epidermal cancers, as well as leukemia and melanoma.2, 8, 50, 51, 52 Data from in vivo animal or clinical studies are lacking.
Quercetin induced a reduction in acetylcholine-evoked release. The mechanism of action may be associated with an interaction with presynaptic calcium channels. In animal models, P. guajava extracts exhibited dose-dependent antinociceptive effects in chemical and thermal tests of analgesia in mice. In another study, the antinociceptive effect of P. guajava extracts was similar in potency to the nonsteroidal anti-inflammatory drug mefenamic acid and 10 times less potent to the opioid analgesic morphine.2, 53, 54 Data from clinical studies are lacking.
Guava is commercially available in capsules, liquids, powders, and tablets.
Eight hourly doses of guava extract standardized to 1 mg of quercetin per 500 mg capsule for 3 days was used in 1 clinical trial16; 10 mL of P. guajava tincture in water taken every 8 hours has also been used.2
Decreases in dysmenorrheal pain intensity were found after 4 months of daily guava leaf extract standardized at 6 mg of flavonoid content per day.2
Hyperlipidemia and hypertension
Pregnancy / Lactation
Information regarding safety and efficacy in pregnancy and lactation is lacking.
Case reports of interactions are lacking. There is a theoretical risk for potentiation of medicines used in diabetes and antidiarrheal medications.25
Acute toxicity tests in rats and mice have found the median lethal dose of guava leaf extracts to be more than 5 g/kg. In vitro genotoxicity and mutagenicity tests on P. guajava in human peripheral blood lymphocytes found no disturbances in cell division or hemolysis.2, 45, 55, 56
Despite experiments suggesting hepatoprotective effects,2, 27, 57 intraperitoneal administration of ethanolic leaf extracts in rats has resulted in increases in serum liver enzymes, an effect that may be dose dependent.2, 57, 58 No histological evidence of hepatotoxicity has been observed.2
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