Banaba

Scientific Name(s): Lagerstroemia speciosa (L.) Pers.
Common Name(s): Banaba, Crepe myrtle, Pride of India, Queen's crepe myrtle, Queen's flower

Botany

Banaba is a deciduous, tropical, flowering tree that grows in India, Southeast Asia, and the Philippines. It typically grows 5 to 10 m in height, and sometimes up to 20 m. The smooth, large, spatulate, oblong to elliptic-ovate leaves measure 4 to 8 cm in width and 12 to 25 cm in length. The flowers are pink to purple when in bloom, and give way to oval, nut-like fruits; the leaves turn orange-red in the fall. The bark of the tree is smooth, grey to cream colored, and peels off in flakes.1, 2, 3

History

Banaba has been used as a folk medicine to treat diabetes in various parts of the world, especially in the Philippines and Southeast Asia. Folkloric use of banaba leaf decoctions for diuretic and purgative purposes and of root parts for stomach ailments has also been recorded. The first published research study evaluating the insulin-like activity of an aqueous extract of dried leaves given to rabbits was reported in 1940; since then, studies evaluating banaba for treatment of diabetes have been conducted in animal models, humans, and in vitro laboratory settings.3, 4

Chemistry

Banaba leaves contain ellagic acid derivatives.5 Reports have confirmed the presence of ellagitannins, lagerstroemin, flosin B, and reginin A, all possible glucose transport enhancers.6 Lagertannins, beta-sitosterol, stigmasterol, campesterol, and some olefins also have been found in banaba leaves and extracts.6, 7, 8, 9 Lageracetal (1,1-Dibutoxybutane), 1-pentanol, ellagic acid, and corosolic acid (a triterpene) have been isolated from the leaves.10, 11 One study reports that 16 amino acids, pyrogallol tannins, and lipids are also present in banaba leaf.12 Nonacosane, hentriacontane, tritriacontane, olefins, and esters of palmitic, daturic, stearic, arachinic, and behenic acids were identified from the neutral fraction of hot ethanol extracts of banaba leaves.13

Banaba bark contains similar constituents to its leaves. One report found ellagic acids, beta-sitosterols, and colosolic acids in bark extracts.14

L. speciosa seeds contain caprylic, lauric, myristic, palmitic, steric, arachidic, behenic, lignoceric, oleic, and linoleic acids in the oil15; 9-keotoctadec-cis-11-enoic acid has been isolated from the seed oil as well.16 Chemical investigation of amino acid components in banaba seed oil has been performed.17 The components nonanedioic acid, 12-acetyloxy-9-octadecenoic acid, and 16-methyl-heptadecandic acids, present in the seed extracts, have been identified as having antibacterial activity.18

L. speciosa and related species contain ellagic acid, campesterol, stigmasterol, and beta-sitosterol in their stem parts.19

Uses and Pharmacology

Animal and clinical studies have demonstrated hypoglycemic effects of both the aqueous and methanol extracts; most studies have focused on corosolic acid. The water-soluble tannin fractions (ie, ellagitannins) may provide antioxidant, anti-inflammatory, insulin-like, and glucose regulatory activities.4

Anti-inflammatory

Animal data

Anti-inflammatory activity in mice has been reported.8 Insight into the anti-inflammatory mechanism of action of banaba may be gained from results of an in vitro experiment in a cardiomyocyte cell line in which an aqueous extract blocked activation of nuclear factor-kappaB by tumor necrosis factor in a time-dependent manner.4 Corosolic acid demonstrated effective anti-inflammatory activity against arachidonic acid and 12-O-tetradecanoylphorbol-13 acetate, as assessed in vivo using a mouse ear assay.4, 20

Clinical data

Research reveals no clinical data regarding the use of L. speciosa as an anti-inflammatory agent.

Diabetes

Animal data

In various reports, the constituent corosolic acid was shown to be a glucose transport activator, suggesting antidiabetic activity. Further investigation has revealed valoneaic acid dilactone as the amylase inhibitor. The ellagitannins lagerstroemin, flosin B, and reginin A increased glucose uptake by rat adipocytes.6, 11, 21

Another report observed inhibitory effects of banaba on postprandial hyperglycemia via inhibition of alpha-amylase and alpha-glucosidases.22, 23

Banaba extracts have been examined in several rodent studies, with reported beneficial effects on blood glucose levels and obesity.24, 25, 26, 27

Clinical data

Reviews of medical literature on the effects of banaba in diabetes have identified few quality clinical trials and a number of open-label or small clinical studies.2, 4, 28

One small clinical trial (N=10) involving patients with type 2 diabetes reported that banaba extract standardized to 1% corosolic acid and administered for 10 days reduced blood glucose levels.29 In a small, open-label study (N=15), 100 mg of a water-soluble banaba extract administered for 1 year produced a significant decrease (16.6%) in fasting blood glucose in individuals with blood glucose levels greater than 110 mg/dL. Improvements in both glucose tolerance and glycated albumin were observed after 6 months, as well as after 1 year of treatment.4

Data from other unpublished studies and reports are generally supportive of a role for banaba in treating diabetes; however, additional quality clinical trials are required before definitive statements or recommendations can be made.2, 4 Other studies have evaluated banaba in combination with other natural products.4, 28 For example, a combination of cinnamon and banaba improved insulin resistance in patients with impaired glucose tolerance.30 Clinical trials evaluating antiobesity effects are lacking.

Other uses

Banaba aqueous extract was shown to have potent radical scavenging activity, in a concentration-dependent manner, on 1,1-diphenyl-2-picrylhydrazyl radical and superoxide radicals generated by a hypoxanthine-xanthine oxidase system. Additionally, lipid peroxidation was inhibited in a rat liver homogenate system.31, 32 Further antioxidant activity has been reported.4, 33, 34, 35

Other reported activities of banaba preparations include antibacterial, antifungal, and antiviral.4, 18, 35, 36, 37, 38, 39 Protection of HIV-infected cells by ellagic acid constituents, possibly via inhibition of reverse transcriptase and HIV protease, has been reported.14, 40

Various in vitro studies report effects of corosolic acid on a variety of human tumor cells.4, 41 In vitro, valoneic acid, a constituent of banaba, has demonstrated xanthine oxidase–inhibiting activity.2

Dosing

Diabetes

Limited clinical trial data exist to provide dosing recommendations. Doses of 32 mg or 48 mg of the standardized extract from L. speciosa leaves (Glucosol) (standardized to 0.32 and 0.48 mg of corosolic acid, respectively) were given daily for 10 days in one small study.29

Pregnancy / Lactation

Avoid use. Information regarding safety and efficacy in pregnancy and lactation is lacking.

Interactions

A case report exists of nephrotoxicity in a diabetic patient, potentially related to an interaction with diclofenac.42

Hypoglycemic drugs, insulin: Banaba has been shown to produce insulin-like actions and may have additive effects if taken concomitantly with diabetic drugs.2 Anticoagulant/Antiplatelet drugs: Antithrombin activity has been reported for the related species L. indica.2

Xanthine oxidase: Aqueous extracts from the plant leaves may have an additive effect in the treatment of hyperuricemia.2 An extract of banaba has been shown to inhibit the sulfation of dopamine and ritodrine, with a 50% inhibition at concentrations of 16 and 7.5 mcg/mL, respectively. The bioavailability of drugs detoxified by intestinal sulfotransferase 1A3 may be increased by banaba.4

Adverse Reactions

No adverse effects have been reported; clinical trials are lacking to provide information regarding adverse effects.4, 43 Use caution in patients with diabetes due to the potential of banaba to lower blood sugar.2

Toxicology

No toxicity has been reported, even in high doses.44 In one report, large oral doses did not produce toxic effects or convulsions.45

References

Disclaimer

This information relates to an herbal, vitamin, mineral or other dietary supplement. This product has not been reviewed by the FDA to determine whether it is safe or effective and is not subject to the quality standards and safety information collection standards that are applicable to most prescription drugs. This information should not be used to decide whether or not to take this product. This information does not endorse this product as safe, effective, or approved for treating any patient or health condition. This is only a brief summary of general information about this product. It does NOT include all information about the possible uses, directions, warnings, precautions, interactions, adverse effects, or risks that may apply to this product. This information is not specific medical advice and does not replace information you receive from your health care provider. You should talk with your health care provider for complete information about the risks and benefits of using this product.

This product may adversely interact with certain health and medical conditions, other prescription and over-the-counter drugs, foods, or other dietary supplements. This product may be unsafe when used before surgery or other medical procedures. It is important to fully inform your doctor about the herbal, vitamins, mineral or any other supplements you are taking before any kind of surgery or medical procedure. With the exception of certain products that are generally recognized as safe in normal quantities, including use of folic acid and prenatal vitamins during pregnancy, this product has not been sufficiently studied to determine whether it is safe to use during pregnancy or nursing or by persons younger than 2 years of age.

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