Medicinal usage of mulberry leaf dates back at least 2000 years. It is mentioned
1. Mulberry has long been consumed for medicinal properties
2. DNJ is the key compound of mulberry leaf that inhibits α-glucosidase therefore lowering blood glucose levels
3. Mulberry is also effective in reducing fat accumulation in obese animals
4. Other compounds of mulberry are also involved in decreasing blood glucose levels
5. Mulberry leaf is safe in toxicity test in rats
in the traditional text, “Divine Farmer’s Materia Medica” (Shen Nong Ban Cao Jing) written in the Western Han dynasty, between 300 BCE and 200 CE.
In Traditional Chinese Medicine (TCM) mulberry leaves posses sweet, slightly bitter, and slightly cold properties. Their primary uses are “to expel wind and heat from the lungs, as well as to clear the liver and the eyes”.
The most exciting thing about mulberry leaf extract is that it has been historically used and recently studied in some Asian countries for blood sugar management. This specifically relates to the treatment of type II diabetes.
The benefits of the mulberry leaf extracts are linked to a compound called 1-deoxynorjirimycin (DNJ) and some of its derivatives. These compounds are reported to inhibit the activity of the carbohydrate digesting enzyme α-glucosidase. Inhibition of α-glucosidase is the foundation of many treatments developed for type II diabetes. Mulberry DNJ also has a positive effect on fat tissue, specifically enhancing expression of adiponectin mRNA in white adipose tissue and suppressed lipid accumulation in rat liver. Therefore DNJ may be therapeutically useful in the treatment of obesity as well as diabetes (1). In an animal study, mulberry was given to obese mice for 12 weeks, mulberry decreased both the visceral fat weight and adipocyte (fat cells) size (2).
Other compounds of mulberry leaf have also been studied for their roles in anti-diabetic activity. An in vivo study was conducted on type II diabetic rats. The activity of an extract of mulberry leaf and its three major constituents, chlorogenic acid, rutin and isoquercitrin were determined. After 11 days of administration of 250 or 750 mg/kg of mulberry leaf extract or corresponding amounts of each individual compound, a dose dependent decrease of non-fasting blood glucose levels were found for mulberry extract, chlorogenic acid and rutin, but not for isoquercitrin. Based on the results, chlorogenic acid and rutin might account for as much as half the observed anti-diabetic activity of mulberry leaf (3).
Safety of Usage. The safety of mulberry has been evaluated by a single-dose oral toxicity study and a 90 day repeated-dose oral toxicity study in Sprague-Dawley rats. The results of the genetic toxicology assays were negative in all of the assays. The approximate lethal dose in single oral dose toxicity study was considered to be higher than 5000 mg/kg. The 90 day repeated-dose study demonstrated that at doses up to 2000 mg/kg/day is safe and does not cause adverse effects (4).
(1). Nakagawa K: Studies targeting α-glucosidase inhibition, antiangiogenic effects, and lipid modification regulation: background, evaluation, and challenges in the development of food ingredients for therapeutic purposes. Biosci Biotechnol Biochem. 2013;77(5):900-8. Epub 2013 May 7.
(2) Tsuduki T, et al: Intake of mulberry 1-deoxynojirimycin prevents diet-induced obesity through increases in adiponectin in mice. Food Chem. 2013 Aug 15;139(1-4):16-23.
(3) Hunyadi A, et al: Chlorogenic Acid and Rutin Play a Major Role in the In Vivo Anti-Diabetic Activity of Morus alba Leaf Extract on Type II Diabetic Rats. PLoS ONE 7(11): e50619, 2012.
(4) Hyun-Suk Heo, et al: Evaluation of General Toxicity and Genotoxicity of the Silkworm Extract Powder. Toxicol. Res. Vol. 29, No. 4, pp. 263-278, 2013.