This article – which was especially technical – discusses guava leaf as having beneficial effects on diabetic myocardium, a cardiac complication stemming from diabetes. The authors state “the aim of the present study was to evaluate the antiglycative as well as cardioprotective role of P. guajava extract in diabetic animal models” (91). A serum protein as cardiac isoform α-2 macroglobulin (cardiac α-2M) was suggested to be involved in the development of cardiac hypertrophy in rats.

“Diabetic complications often arise “as a result of non-enzymatic protein glycation which leads to the formation of advanced glycation end products (AGE’s). The non-enzymatic condensation reaction between the reducing sugars, such as glucose and the amino side chains in proteins (also called Maillard reaction or glycation) has been shown to play an important role in the development of chronic complications of diabetes mellitus” (91). Since guava leaves have been shown to help combat the formation of AGE’s, they thought they would see if a guava leaf extract would help keep the rats who had diabetes from forming these cardiovascular complications.

Using rats as models, the scientists induced diabetes by a “single intraperitoneal (body cavity) injection of STZ (strdissolved in citrate buffer…for three days (92). After the three day period, only rats with fasting blood glucose level above 200mg/dl were considered diabetic and included in the diabetic model.

As the abstract states: “Daily administration of the extract for a period of one month significantly decreased the blood glucose, glycated hemoglobin and fructosamine levels in a dose dependent manner, and the authors conclude that  “These findings support that the administration of PGEt [guava leaf extract] extract may be beneficial for preventing cardiovascular complications associated with diabetes.”

I’ve been working to gather the latest research published on guava leaf extract, and am in the “digestion” process currently – sounds bad, but it’s true. It takes a bit of time for me to read, and re-read the studies to ensure that I can report accurately on them. The latest one I’ve been reading is “The Beneficial Effects of Psidium guajava leaf extract on diabetic myocardium,” out of Experimental and Toxicologic Pathology. I realize that it’s been a while since I’ve posted on a study, but there is more to come, I promise. Look for the full write-up tomorrow.

Thanks everyone!

Kristina

My Intro to Guava Leaf Extract

Truth is though, from all the studies I’ve read so far, and from what I can tell sifting through article after article online, plants have lots to offer aside from just “nutrition.” Guava leaf isn’t the only plant to have seemingly amazing and unbelievable effects, but it is the only one that I’ve had any sort of personal relationship with.

In trying to prepare to write my first book, and to get back to writing after about five years hiatus, I read a book about Ginseng. In this book, “The Book of Ginseng, and other Chinese Herbs for Vitality” by Stephen Fulder, the differences between the Eastern and Western models of health and well-being are explored. He states that “while Western medicine can provide many cures for obvious disease, it is incompetent in dealing with…states of chronic sub-health. This is the practical consequence of defining health as the absence of sickness” (45). In Eastern, or Chinese medicine, “Diseases arise through imbalances, health through equilibrium, and medicine and its drugs are essentially adjustive and restorative” (44).

Western Medicine

Western medicine has become very adept at dealing with disease once it presents itself, and pharmaceutical companies are at the helm of drug discovery process for this method of healing. Natural products have long been a focus for many pharmaceutical companies, often with promising outcomes. Drug discovery from medicinal plants led to the isolation of early drugs such as cocaine, codeine, digitoxin, and quinine, in addition to morphine. Many of these early drug discoveries are still in use (Kinghorn 2005).

A continuing issue for these pharmaceutical companies remains however: drug discovery through natural products can be both costly and time-consuming, due to the complex nature of the chemical compounds found in plants. In the late 1980’s and early 1990’s, competition between pharmaceutical companies to come up with novel classes of drugs prompted them to find a way to speed up the drug discovery process. This led to the breakthrough development of high-throughput screening (HTS), which in turn led to what the industry calls ‘blitz-screening,’ in which a drug can be tested in three months’ time.

Medicinal Plants

Because medicinal plants are structurally complex, chemists often prefer not to work with them because it is difficult to prepare as many natural product analogs as synthetic chemicals in the same amount of time. Even with these limitations, drug discovery from natural products continues; in the areas of cancer and infectious disease, for example, 60% and 75% of new drugs, respectively, originated from natural sources between 1981 and 2002. Between 2001 and 2005, 23 new drugs derived from natural products were introduced for the treatment of disorders such as bacterial and fungal infections, cancer, diabetes…the list goes on. In both 2001 and 2002, approximately one quarter of the best-selling drugs worldwide were natural products or derived from natural products (Butler 2000). Despite the success of natural products as a source for new drug leads, however, many large pharmaceutical companies have downgraded or even terminated their natural product research programs (Lam 2007), in part because of the lack of profitability and quick turnover rates cited above.

During much of the 20th century, medicinal plants were regarded with skepticism and the practice of herbal medicine went into decline. Plants were viewed mainly “as a potential source of pure chemical compounds for the development of medicine” (Gurib-Fakim 2006).  Perhaps this trend will begin to turn around as the benefits of plants are gaining recognition worldwide.

For guava leaf tea, you can use either method – to ensure the maximum amount of phytochemicals are extracted, simmer for a minimum of 10 minutes.  If using dried leaves, add a couple teaspoons per each 8oz water to start, then alter to personal taste.  If using fresh leaves you need to add more (maybe 2-4tsp), as the leaves will not be as concentrated and still contain a great deal of water.

These methods may be used for a variety of medicinal teas, but be sure to research your ingredients.  Guava leaf has not been shown to have any toxicity, so making a very strong guava leaf tea is ok.  The same cannot be said for all herbs.  As always, make sure to discuss all herbal uses with a medical professional to asses medication interactions and health concerns.

Cheers to your health, everyone, and I appreciate your comments and questions.  Keep them coming!

This paper “reports the in vitro studies [studies done in a petri dish] of the activity of 16 plant extracts against pathogenic enterobacteria (31).  The researchers start out with a list of 408 plants; they narrow the list down to 34 plants which are deemed worthy of further study.  Of these 34 plants, 16 are chosen for “confirmation” of antibacterial activity against E coli, Salmonella enteritidis, and Shigella flexneri pathogens.  Guava leaf (Psydium guajava) turns out to be one of three plants (out of the 16) that inhibits growth of all three kinds of bacteria.

For a majority of these plants, the most effective extraction agent for antibacterial activity is ethanol.  Ethanol extract, acetone extract, and n-hexane extracts of each plant are tested and compared for effectiveness.  For guava leaf, the acetone extract proved most effective for antibacterial activity.

In Guatemala, guava leaf is used for diarrhea, dysentery, stomach pain, leucorrhea (a condition of unusual vaginal discharge), and a variety skin infections.

To access this article, please click here.

The study on the hepatoprotective effects of guava leaf extract was conducted at the Krupanidhi College of Pharmacy in Bangalore, India.  Researchers collected fresh leaves from guava trees in the Koramangala area in Bangalore.  They crushed them, and boiled the leaves in water for one hour.  They filtered out the solids, and evaporated the water, leaving a powdered guava leaf extract.  Rats were used as study subjects.

Analysis of the extract showed that it contained carbohydrates, tannins, flavanoids, saponins, steriods, protiens and amino acids.

Researchers found that the extract showed good liver protective activities; the effect produced by the higher doses of guava leaf extract (500mg/kg) was similar to that produced by Silymarin, a well-known hepatoprotective agnet.  Furthermore, the guava leaf extract prevented an increase in liver weight in rats, something Silymarin does not do.

“In conclusion,” the researchers stated, “the aqueous extract of Psidium guajava Linn. leaves [guava leaves] showed good hepatoprotective activity in CCI4 induced acute and chronic liver damage, PCM induced liver damage and TAA induced liver necrosis.  The hepatoprotective activity may be due to the antioxidant effect of the plant” (310).  In other words, guava leaves can help protect the liver.  Guava leaf tea or guava leaf extract seems to be able to help prevent damage, or help to treat damage already done.

For a link to the full article, please click here.

In the article, an ”aqueous extract of Psidium guajava L budding leaves (PE) has been shown to possess anti-prostate cancer activity in a cell line model” (260).  The researchers reported that they were drawn to study guava leaves’ effect on prostate cancer cells after conducting a study which showed that guava leaves were “potent anti-glycative agents” (261); this action was ascribed to the unusual free radical scavenging and anti-oxidative capabilities of guava leaf polyphenols.  The effects of glycation can result in the formation of irreversible advanced glycation end products (AGE’s), which are associated with many progressive diseases and can also trigger cancer formation.  Since guava leaves showed strong anti-glycative properties, the scientists chose to study the leaves’ action against an abundant form of prostate cancer, LNCap: Lymph node-metastasis prostate cancer.

They performed tests both in vitro (petri dish) and in vivo (in mice).  In vitro, they found that guava leaves were cytotoxic on the cancer cells, and that the leaves ”arrested cell cycle of LNCaP cells…[guava leaves] inhibited LNCaP cell growth and proliferation by preventing the cells from entering the S phase, and…TUNEL assay also confirmed the apoptic mechanism induced by [guava leaves]” (265).

In vivo, “although no significant difference in body weight was observed among the tumor-implanted [mice], the size of the tumors in the untreated mice was much larger when compared to tumor sizes in the guava leaf-treated mice at week 6 of the study.

“Conclusively,” the authors state, “[guava leaf] is a potent anticancer agent, acting through both cytotoxic and apoptotic action mechanisms; therfore, it [can feasably be used] as a potential adjuvant anti-prostate cancer therapy, in particular, for anti-androgen-responsive PCa” (268).

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