Shedding the Truth behind the Leaves – Nature is the Best Healer
Hderbert Arellano, MD
The very foundation of ancient medicine was heavily invested in natural remedies; and while many ancient practices have been lost in time as medical knowledge advanced, some of these ancient secrets have lived on to the present. Chamomile tea for headache, garlic cloves for allergies, guava leaves for infected wounds – just to name a few. Even modern scientists find the most peculiar of cures in the oddest of places – from French lilac blossoms, to the saliva of the Gila monster, to the humble apple tree bark.
It’s not surprising that even in these modern times, many people are constantly looking for remedies from nature and, despite scientific evidence, subscribe to the notion that “natural” or “herbal” remedies are better. Too often I found myself asked by patients with diabetes during consultation if they could try herbal remedies that they see on TV or hear about from their friends. At first it was a struggle trying to earnestly address such inquiry; but nowadays, I feel like my responses are becoming more defensive and sometimes condescending. How could mango leaves or malunggay possibly decrease blood glucose level? And what on earth is an insulin plant? I simply couldn’t wrap my head around that. Am I missing something? The amount of queries I get was getting hard to ignore, so I finally gave in and decided to investigate.
A quick search of the databases led me to articles about a certain plant from the genus Costus. Native to South America but widely cultivated in Western Ghats of India, this shrub is used by local folk healers to treat diabetics, a practice rooted in the Siddha and Ayurveda medicine.
Costus igneus—or the so-called insulin plant—gets its name from its apparent blood glucose-lowering properties and is believed by alternative healers to be as equally potent as anti-diabetic medications like sulfonylureas. The scarcity of clinical data makes it hard to substantiate such claim, but one study by Dr. Shetty and his colleagues demonstrated that extract from C. igneus leaves was able to counter the impact of steroids on blood glucose levels among Wistar rats similar to glibenclamide, both in fasting and after meal conditions. Different authors reported comparable findings on the effect of ethanol extracts for the leaves of this plant among other drug-induced (alloxan and streptozotocin) diabetic rat models. Furthermore, the group of Dr. Joshi in India has isolated an insulin-like peptide (ILP) from purified C. igneus extract with glucose-lowering effect in-vitro and in murine (rat) models. Their experiments showed that ILP raises IRS-1 expression with concomitant increase in GLUT-4 translocation, reminiscent of insulin signaling. Other substances isolated from another species of Costus C. pictus such as bixin, norbixin, and geraniol, are said to be activators of the peroxisome proliferator-activated receptor (PPAR) similar to the drug rosiglitazone, and demonstrated similar glucose and lipid lowering properties. It has also been suggested that these substances may also lessen oxidative stress and advanced glycation end-products (AGE), which are implicated in the development of diabetes-related complications. However, these findings remain limited to the murine family; and whether or not such observation will translate well into human physiology remains theoretical. Until empirical evidence proves otherwise, it’s difficult not to have reservations on the right matter.
Mango is well known for its succulent fruit, but the leaves of the Mangifera indica is enormously popular among herbalist and nutraceutical advocates. Its leaves can be boiled into tea or purified into Mangifera indica kernel flour (MIKF) and has been traditionally used in Ayurvedic practices and in Filipino culture. Pre-clinical studies using MIKF in streptozotocin-induced diabetic rats showed comparable decrease in blood sugar levels to that of metformin, the first-line drug in treatment of diabetes. MIKF is said to be a rich source of flavonoids and phenolic acids that may have inhibitory effect towards key enzymes (i.e. α-amylase, α-glucosidase, and aldose reductase). Ethanol extracts were also shown to be protective against hyperglycemia in alloxan-induced rat model, while seed kernel extracts were found to be similarly effective in treating streptozotocin-induced rat models. Lyophilized M. indica extracts have also been shown to inhibit dipeptidyl peptidase 4 (DPP4), one of the targets of current diabetic pharmacotherapy. Antioxidant, leptin and endothelin-1 modulatory effects have also been cited in literature. However, no human trial using either seed kernels, MIKF or ethanol extracts has been conducted; and just like the insulin plant, it’s a long way to go before possible human application.
Horseradish tree (Moringa oleifera), locally known as malunggay in the Philippines, is not only popular for its distinct flavor in Asian cuisine but also its role in traditional medicine. Like the insulin plant, extracts from malunggay leaves have been demonstrated to have anti-hyperglycemic properties in several diabetic rat models, possibly from its rich terpenoid content. Antioxidant and lipid-lowering properties were shown in animal studies as well. Interestingly, one particular study using alloxan-induced diabetic rat model showed that co-administration of moringa extract with the diabetes drug sitagliptin showed decreased glucose-lowering efficacy of the latter.
Five small-scale human trials (n=6-60) using whole leaf powder have been conducted since 1993, demonstrating modest glucose-lowering effect among subjects with type 2 diabetes. However, there was significant heterogeneity in dosing strength and treatment duration among the studies that made it difficult to identify an optimal or standard regimen. The studies were also of short duration and lacked reports on important safety data. Although initial data appear to be promising, additional human studies with larger population and longer observation period are needed, as well as additional investigation on possible interactions with other standard diabetes medications.
Right now, we live in a world where the next big cure could be waiting in our backyards, or sitting in the fridge or at the back of our countertops, bidding its time to be discovered. It would not hurt to keep an open mind but coupled with the sensibility to discern science from superstition, fact from fad. It seems to me that today may not be the time for these herbs; but ten minutes in boiling water, I’m sure these leaves will make a great tea.
REFERENCES: Shetty et al. International Journal of Ayurveda Research. 2010; Joshi et al. Biochem Biophys Res Commun. 2013. Vishnu et al. Journal of Pharmacy Research. 2010. Hardikar et al. Phytochemistry. 2016. Annadurai et al. BMC Genomics. 2012. Irondi et al. Food Science & Nutrition. 2016. Yogisha et al. Journal of Natural Products. 2010. Sharma et al. Int J Pharm Bio Sci. 2013. Gupta et al. Diabetologia Croatica, 2011. Stohs et al. Phytotherapy Research. 2015. Olurishe et al. J Ethnopharmacol. 2016.
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