Guava (Psidium guajava), an important food crop and medicinal plant in tropical and subtropical countries is widely used like food and in folk medicine around of the world. In many parts of Africa, the leaf, stem-bark, and roots of guava are used traditionally for the management, control, and/or treatment of an array of human disorders.

Guava fruits and leaves

Ancestral medicinal use of guava today is however supported by numerous biomedical studies concerning the properties of leaf extracts. Guava leave is used traditionally in African folk medicine for several ailments, including diabetes mellitus, diarrhoea, cough, painful menses, and hypertension. It is also used to treat tooth decay, gum infection, sore throat, to disinfect wounds and as an antiseptic.

For instance, the Southeast Nicaraguan indigenous communities of Cuna and Waunana, make a tea from the leaves and bark of the guava for treatment of diarrhoea and dysentery, while the Sumu, Panamahka, Twahka, Ulwa, and Bawihka tribes use it for upset stomachs, vertigo, and to regulate menstrual cycles.

In India, decoction of the leaves and bark of guava is used to cure diarrhoea, dysentery, vomiting and sore throats, and to regulate menstrual cycles. The tribes of the Amazon use leaf decoction for mouth sores, bleeding gums, as douche for vaginal discharge and to tighten and tone up vaginal walls after labour.

Some of the anecdotal, folkloric, ethno medical uses of guava leaves and bark has been scientifically appraised by experts and found they indeed have there scientific basis under experimental paradigms. A study in the 2005 edition of the American Journal of Chinese Medicine assessed the effect of using the extract of guava leaves and Juglans regia (walnut) leaf extracts to germs that cause pimple(acne), and found it to be beneficial in treating pimples on the face, especially when they are known to have anti-inflammatory activities

The study was done by Qadan F, Thewaini AJ, Ali DA, Afifi R, Elkhawad A, Matalka KZ., all from the Faculty of Pharmacy and Medical Technology, The University of Petra, Amman, Jordan. It enrolled 38 men and women with pimples on their faces.

They cultured acne-causing bacteria Propionibacterium acnes (P. acnes) as well as Staphyloccocus aureus and epidermidis from 38 acne patients. They then tested the effectiveness of these extracts of guava and walnut leaf in killing acne-causing bacteria.

It found that these two extracts have significantly better antimicrobial effects on the Staphyloccocus bacteria in vitro (or in test-tube environments) as compared to tea tree oil, as well as doxycycline and clindamycin antibiotics. However, it has lower antimicrobial activities on P. acnes, as compared to the chemical antibiotics.

There are many over-the-counter (OTC) preparations for treatment of acne. Sold as lotions, gels, creams, and cleansers, OTC products can be unsafe to buy because of the potential adverse effects chemical agents have on natural skin.

This is especially true for skin conditions like acne, where the use of harsh chemicals could further worsen the matter. Therefore, an alternative treatment for acne was needed. This created a great interest towards the possible effect of natural substances that are obtainable from medicinal plants that have antibacterial and anti-inflammatory activity, which are commonly employed for the treatment of acne.

Its use to treat painful menses was substantiated by another study titled: “Effect of a Psidii guajavae folium extract in the treatment of primary dysmenorrhoea: A randomised clinical trial” which was published in the March 2007 edition of the Journal of Ethnopharmacology.

A double-blinded randomised clinical trial was conducted in 197 women with primary dysmenorrhea. Four intervention groups were defined: two extract doses (3 and 6 mg/day); ibuprofen (1200 mg/day); placebo (3 mg/day). Participants were followed-up individually for four months. The main outcome variable was abdominal pain intensity measured according to a visual analogue scale (VAS).

The average age of participants was 19 years; they started menstruation about the age of 12 years. Participants had menstrual cycles of 28 or 29 days, with menstruation lasting five days and mean of pain intensity of 8.2 on the VAS. During each successive treatment cycle, participants experienced a lower pain intensity score.

After adjusting each cycle for baseline pain, treatment compliance and other variables, the group receiving 6 mg/day extract had significantly reduced pain intensity while the group receiving the 3 mg/day extract did not show a consistent effect throughout the three cycles.

They concluded that at a dose of 6 mg/day, the standardised phyto-drug (Psidii guajavae folium extract) reduced menstrual pain significantly compared with conventional treatment and placebo. In addition, the traditional use of guava in the treatment of such ailments like diabetes and hypertension was corroborated by another study by Ojewole JA from the University of KwaZulu-Natal, Durban, South Africa.

The results of the experimental animal study titled “Hypoglycemic and hypotensive effects of Psidium guajava Linn. (Myrtaceae) leaf aqueous extract,” indicated that the leaf aqueous extract of guava leaves possess hypoglycemic and hypotensive properties, and thus lend pharmacological credence to the suggested folkloric, ethno-medical uses of the plant in the management or control of adult-onset, type 2 diabetes mellitus and hypertension in some rural African communities. .

Although the exact mechanisms of action of the plant’s extract still remain speculative at present, but it was suspected that its numerous chemical compounds constituents such as the tannins, polyphenolic compounds and flavonoids, account for the observed effects of the plant’s leaf extract.

Guava leaf tea of guava is commonly used as a medicine against gastroenteritis(Dysentry) and child diarrhoea by those who cannot afford or do not have access to antibiotics. A study that screened the antimicrobial effect of essential oils and methanol, hexane, ethyl acetate extracts from guava leaves against diarrhoea-causing bacteria: Staphylococcus aureus, Salmonella spp. and Escherichia coli.

The essential oil extract showed ability to kill some of these diarrhoea-causing germs like S. aureus and Salmonella spp. thus supporting the use of guava leaf extracts and essential oil in cases where access to commercial antibiotics is restricted.

The Brazilian researchers said guava leaf extracts and essential oil could be important potential sources of new antimicrobial compounds, according to the study published in the 2008 edition of the Rev Inst Med Trop Sao Paulo.

Garlic not effective for cholesterol control

A study from Stanford University casts doubt on the effectiveness of garlic to lower LDL (low density lipoprotein) cholesterol levels in adults with moderately high cholesterol. LDL cholesterol is widely known as “bad cholesterol,” and is believed to be a leading contributor to heart disease.

Christopher Gardner, Ph.D., and colleagues conducted a randomized, placebo-controlled trial studying whether three different formulations of garlic could lower LDL cholesterol. The study participants were randomly divided into four groups to receive raw garlic, a powdered garlic supplement, an aged extract supplement, or a placebo.

The 169 participants who completed the study had their cholesterol levels checked monthly for the duration of the 6-month trial. None of the formulations of garlic had a statistically significant effect on the LDL cholesterol levels.

The authors caution that these results should not be generalized for all populations or all health effects. An accompanying editorial in the journal Archives of Internal Medicine points out that LDL cholesterol levels are only one factor contributing to heart disease, and that this trial did not investigate garlic’s effects on other risk factors, such as high blood pressure.

Christopher D. Gardner, Larry D. Dawson, Eric Block, et al. Effect of Raw Garlic vs. Commercial Garlic Supplements on Plasma Lipid Concentrations in Adults With Moderate Hypercholesterolemia: A Randomized Clinical Trial. Archives of Internal Medicine, February 2007