Guava
Scientific Name(s): Psidium guajava L. Family: Myrtaceae
Common Name(s): Guava (in English), guayabo (in Spanish), goiabeira (Brazil), red guava , guyava , kuawa 1 , 2 , 3
Clinical Overview
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Uses of Guava
Scientific investigations on the medicinal properties of guava leaf products date back to the 1940s. Most scientific evidence examines the clinical efficacy of guava in treating GI disorders. Other investigations examined antiamebic, antibiotic, antidiarrheic, antihyperglycemic, antimutagenic, antispasmodic, and sedative effects, as well as anticough and narcotic-like activities of the plant species. A randomized double-blind study of 122 subjects documented P. guajava leaf extract to be as effective as tetracycline in treating acute infectious diarrhea.
Guava Dosing
One trial used the P. guajava extract QG-5 , which is standardized to contain quercetin 1 mg per 500 mg capsule. Patients with infectious gastroenteritis received 1 capsule of QG-5 orally every 8 hours for 3 days. Guava is commercially available in capsules, liquids, powders, and tablets.
Contraindications
Hypersensitivity to any of the ingredients in guava.
Pregnancy/Lactation
Avoid use during pregnancy and lactation because of lack of clinical data.
Guava Interactions
None well documented.
Guava Adverse Reactions
Besides constipation, no serious adverse reactions have been reported in patients taking QG-5 .
Toxicology
In vitro genotoxicity and mutagenicity tests on P. guajava in human peripheral blood lymphocytes found no disturbances in cell division.
Botany
P. guajava is a member of the Myrtaceae family, which contains at least 133 genera and more than 3,800 species. 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. Today, the plant is cultivated from the west coast of Africa to the Pacific region, including India and China, 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 mostly consumed fresh. The berry contains several small seeds and consists of a fleshy pericarp and seed cavity with pulp. 2 , 4 , 5
History
P. guajava has a rich ethnomedicinal history. Different parts of the plant are used in various indigenous systems of medicine, primarily for the treatment of GI ailments. 6 , 7
The therapeutic properties of the leaves have been described in detail by historical Mexican herbal sources dating back 500 years. 5
Chemistry
Most phytochemical analyses investigated the properties of guava leaf products, revealing more than 20 isolated compounds, including alkaloids, anthocyanins, carotenoids, essential oils, fatty acids, lectins, phenols, saponins, tannins, triterpenes, and vitamin C (80 mg per 100 g of guava). 6 , 8 , 9 , 10 , 11 , 12 , 13
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. Carbohydrate esters have been isolated from the fruit. 8 , 11
The main active constituent in the plant is quercetin. Spasmolytic and antidiarrheal effects are associated with its quercetin-derived flavonoid glycosides, which support use of this ancient leaf remedy in treating GI disorders. 5
Guava Uses and Pharmacology
Scientific investigations on the medicinal properties of guava leaf products date back to the 1940s. Some investigations examined antiamebic, antibiotic, antidiarrheic, antihyperglycemic, antimutagenic, antispasmodic, and sedative effects, as well as anticough and narcotic-like activities of the plant. However, most scientific evidence relates to the clinical efficacy of guava in treating GI disorders. 5 , 8
The young leaves of the plant have been used as a tonic to treat digestive conditions such as cholera and diarrhea in Brazil and Mexico. Current 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 is prescribed as a febrifuge and a spasmolytic. In Bolivia and Egypt, guava leaves are used to treat cough and pulmonary diseases. Young guava leaves are used to treat cough in India, and in China, the leaves are used as an anti-inflammatory and hemostatic agent. 3 , 4 , 6 , 7 , 8
Guava bark is 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 is used in Africa and Asia to prevent and treat scurvy; it also is used to treat hypertension in the central plateau of Burkina Faso (West Africa). Ethnomedicinal reports document use of the plant in treating malaria. 7 , 9 , 10
Commercially, world production of guava fruit is estimated at about 500,000 metric tons, with Brazil, Colombia, Mexico, and Venezuela producing significant quantities. Processed guava products include beverages, cheese, ice cream, jams, jellies, juice, syrup, toffee, wine, and dehydrated and canned products. 4
Antispasmolytic and antidiarrheal effectActivity is associated with a group of 5 quercetin-derived glycosides. Quercetin affects smooth muscle fibers as a calcium antagonist, inhibits intestinal movement, and reduces capillary permeability in the abdominal cavity. Most of the evidence is derived from in vitro and animal studies. 5 , 14
In vitro and animal dataThe flavonoid quercetin inhibited intestinal contraction induced by different concentrations of calcium on isolated guinea pig ileum, demonstrating a clear calcium antagonistic effect. A guava extract (50 to 200 mg/kg) inhibited the effect of castor oil- (10 mL/kg) induced diarrhea in mice when compared with controls. In the same study, the effect of a guava extract on small intestine motility was comparable with atropine 1 mg/kg. In another experiment in rats, morphine and guava extract produced similar antidiarrheal effects. A dose of 0.2 mL/kg of fresh leaf extract produced 65% inhibition of intestinal propulsion. This dose was comparable with morphine sulfate 0.2 mg/kg. 9 , 15 , 16
The plant has been used in ethnoveterinary medicine in Trinidad and Tobago for treating dogs with diarrhea. 17
Clinical dataP. guajava may be useful in treating infantile rotaviral enteritis. Sixty-two patients with rotaviral enteritis were randomly assigned, and the experimental group was treated with P. guajava . Outcome measures included the time to diarrhea cessation, the content of Na+ in blood, the content of Na+ and glucose in stool, and the rate of negative conversion of human rotavirus (HRV) antigen. Results from all outcome measures support the use of P. guajava . The experimental group recovered 3 days earlier and the rate of negative conversion of HRV in feces was significantly better versus controls (87% vs 58%, respectively, P < 0.05). The time to cessation of diarrhea in the treated group was shorter than in the controls (25 vs 39 hours, respectively). The content of Na+ and glucose in stool also was reduced in the treated group. 18
A randomized double-blind trial examined the efficacy of a standardized P. guajava extract ( QG-5 , estimated quercetin 1 mg per 500 mg capsule) versus placebo in 100 patients with infectious gastroenteritis. The experimental group (n = 50) received 1 capsule of QG-5 orally every 8 hours for 3 days, while the control group (n = 50) received the same regimen with matching placebo capsules. Conventional oral rehydration therapy was initiated in both groups. Outcome measures included number of daily stools, consistency, presence of mucus, degree of abdominal pain, number of spasms in 24 hours, fever, and number of vomiting episodes. Results indicated a significant ( P = 0.02) difference in outcome measures favoring the experimental group, mostly due to an antispasmolytic effect, which helped reduce the number of episodes of abdominal pain. No adverse effects were reported for patients treated with QG-5 . 5
A review of a randomized double-blind study of 122 people documented P. guajava leaf extract to be as effective as tetracycline in treating acute infectious diarrhea. 19
Antimicrobial activityLeaf and bark extracts have in vitro antimicrobial activity mostly associated with flavonoids, such as morin glycosides, quercetin, and quercetin glycosides. In 1 study of 38 patients with various types of acne, the antimicrobial activity was compared with tea tree oil, doxycycline, and clindamycin. 20 , 21 , 22 , 23
In vitro and animal dataThe leaves and stem bark of P. guajava have antiamoebic activity against Entamoeba histolytica . A methanolic extract of P. guajava leaves displayed inhibitory activities against the growth of Salmonella spp. (2 isolates), Shigella spp. ( S. flexneri , S. virchow , and S. dysenteriae ), and enteropathogenic Escherichia coli (2 isolates) such as E. coli O157:H7. Polygalacturonase inhibitory proteins in the plant's cell walls also play a role in resistance to a fungal attack. 7 , 17 , 24 , 25 , 26 , 27 , 28 , 29
Cardiovascular activityAnimal data
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. The mechanism of action may be associated with inhibiting calcium inward current. In a rat animal model, intravenous administration of P. guajava leaf aqueous extracts (50 to 800 mg/kg) produced a dose-dependent reduction ( P < 0.05 to 0.001) in systemic arterial blood pressure and heart rate in hypertensive Dahl salt-sensitive rats. 8 , 30
Clinical dataEvidence from a randomized, single-blind, clinical trial suggests that by adding moderate amounts of guava fruit to the diet, changes in dietary fatty acids and carbohydrates may decrease lipoprotein metabolism and blood pressure. Two groups of patients (N = 120) were assessed over 12 weeks; each group received guava fruit, preferably before meals. Approximately half of the patients had a net decrease in serum total cholesterol (9.9%), triglycerides (7.7%), and blood pressure (9/8 mm Hg), with a net increase in high-density lipoprotein (HDL) cholesterol (8%) after 12 weeks of guava fruit substitution. 31
A single-blind, randomized, controlled trial of 145 hypertensive patients found similar results. Patients received a fiber- and potassium-enriched diet containing 0.5 to 1 kg of guava daily or their usual diet; alcohol, caffeine, cholesterol, fat, and salt intake were similar in both groups. After 4 weeks, systolic and diastolic pressures improved, decreases occurred in serum total cholesterol and triglycerides, and there was a mild increase in the ratio of total cholesterol/HDL-cholesterol in the guava group. 32
A 9-week study examined the effects of consuming guava 400 g/day on total antioxidant status and lipid profile (total cholesterol, triglycerides, low-density lipoprotein [LDL] and HDL cholesterol). Consumption of guava reduced oxidative stress and blood cholesterol levels. 33
Other pharmacological activityGuava has been studied as an ingredient in diabetic diets. Protein tyrosine phosphatase 1B (PTP1B) is a potential therapeutic target in the treatment of type 2 diabetes. Leaf extracts of P. guajava inhibited the activity of PTP1B in animal models. 34 , 35
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. 4 , 36 , 37
P. guajava may have CNS effects. 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. 38 , 39 , 40 , 41
In vitro antiproliferative activity has been reported for P. guajava leaf oil against human mouth epidermal carcinoma with an IC 50 value of 0.0379 mg/mL. 42
Dosage
One randomized double-blind trial used the standardized P. guajava extract QG-5 , which contains quercetin 1 mg per 500 mg capsule. Patients with infectious gastroenteritis received 1 capsule of QG-5 orally every 8 hours for 3 days. 5 Guava is commercially available in capsules, liquids, powders, and tablets.
Pregnancy/Lactation
Avoid use during pregnancy and lactation because of lack of clinical data.
Interactions
No clinical data exists. There is a theoretical risk for potentiation of pharmacologic activity for patients being treated with medications for cholesterol, depression, diabetes, or sleep disorders while also taking P. guajava commercial preparations. P. guajava commercial preparations also may potentiate the pharmacologic activity of antidiarrheal medications. 9
P. guajava leaf extract preparations also may decrease therapeutic activity of alkaloid-based pharmaceuticals and herbs because of the potential interaction with tannins and alkaloids. The tannins in guava also may inhibit iron absorption. 19
Adverse Reactions
Besides constipation, no serious adverse reactions have been reported in patients taking QG-5 . 5
Toxicology
Acute toxicity tests in rats and mice have proven the LD 50 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. 7 , 43
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