Acacia

Most have no recorded medicinal use. The ones that reach commerce or the literature: S. senegal (true gum arabic), S. catechu (catechu, khadira), S. rugata (shikakai, formerly Acacia concinna), S. polyacantha, S. pennata (cha-om, eaten as a vegetable in Thailand and Laos) and S. berlandieri (guajillo, a phenethylamine-bearing browse plant of Texas and Mexico).

The medicinally or commercially notable ones: V. nilotica (babul), V. seyal (talha gum), V. farnesiana (sweet acacia, cassie), V. karroo (sweet thorn, a southern African gum and bark remedy), V. tortilis (umbrella thorn) and V. xanthophloea (fever tree, named for a supposed link with malaria that came from the mosquitoes of the swamps where it grows).

Very few have any use beyond timber, tannin, land rehabilitation and food. The notable ones: A. mearnsii (black wattle, the tannin crop), A. confusa, A. acuminata, A. obtusifolia and A. maidenii (the tryptamine-bearing wattles), and A. victoriae, A. colei, A. murrayana and A. aneura (mulga), whose seed is roasted and ground as wattleseed.

Gum arabic is the dried sap of two thorn trees of Africa’s dry belt, tapped by cutting the bark and collecting the hardened tears. Senegalia senegal grows from Senegal east to Ethiopia and Somalia and south to Natal, and also in Arabia and the Indian subcontinent ^{32Reference 32Fern · 2024Senegalia senegal — habit, range, habitat and uses — species databaseView study →}. In Sudan it is grown in “gum gardens” for gum production ^{32Reference 32Fern · 2024Senegalia senegal — habit, range, habitat and uses — species databaseView study →}.

It is a soluble, slowly fermented fibre, and a 2023 systematic review covers 29 clinical trials ^{1Reference 1Al-Jubori et al. · 2023Systematic reviewThe Efficacy of Gum Arabic in Managing Diseases: A Systematic Review of Evidence-Based Clinical Trials — systematic reviewView study →}. It is described in full on the gum arabic entry.

Sweet acacia, also called huisache, cassie and aroma, is a small thorny tree of Mexico and Central America, now grown across the tropics. In Mexican and Indian folk practice the bark and pods are used as astringents for diarrhoea, wounds and inflamed skin, and the flowers are infused for indigestion.

Its main commercial use is in perfumery. Cassie absolute, extracted from the flowers, has a violet-and-honey scent. It is also sold under the plain name “acacia”.

Several Australian and Pacific wattles carry tryptamine alkaloids in the bark or root bark, most notably Acacia confusa, A. acuminata, A. obtusifolia and A. maidenii. They have no herbal-medicine tradition or therapeutic use. “Acacia root bark” sold online is usually from one of these species rather than any of the medicinal ones.

Some wattles also contain tyramine, which can interact with MAOI antidepressants.

The two main medicinal acacias of India are both Ayurvedic staples. Khadira (Senegalia catechu) is the classical astringent and blood-purifying drug, used for mouth and throat complaints, skin disease and loose stool, and in khadiradi vati lozenges.

Babul (Vachellia nilotica) is used from the bark for much the same complaints: gargles for the gums, washes for wounds, decoctions for diarrhoea and dysentery, and twigs as chewing sticks.

Both are drying, tightening drugs, and both are given short-term.

Gum arabic is a food, a medicine, a trade good and a pharmaceutical ingredient across the Sahel and Arabia. Sudanese and Arabian practice takes it for kidney complaints in particular. Across the Sahel the same trees supply fodder, timber and tannin.

Vachellia nilotica and V. tortilis are used regionally as astringents for diarrhoea, wounds and sore throats.

Western practice adopted the gum rather than the barks. Acacia gum appears in lozenges, syrups, emulsions and demulcent preparations for the throat and digestive tract, and pharmacists long used it as an excipient.

Tannin-rich acacia bark has been used externally as an astringent wash and, in folk practice, internally for diarrhoea.

Australian wattles were used widely as food and material. Seeds from selected species were roasted and ground into flour, the gums were eaten, and bark and leaves were applied in regional remedies. Practice varies greatly between species and communities.

Gum arabic. A large, branched arabinogalactan-protein complex that humans cannot digest but colonic bacteria ferment slowly and distally ^{6Reference 6Kaddam et al. · 2020Clinical trialEffect of Gum Arabic (Acacia senegal) on C-reactive protein level among sickle cell anemia patients — clinical trialView study →}. In vitro gut-simulator models show it selectively raises Bifidobacteria and Faecalibacterium prausnitzii and boosts short-chain fatty acids, particularly propionate and butyrate ^{6Reference 6Kaddam et al. · 2020Clinical trialEffect of Gum Arabic (Acacia senegal) on C-reactive protein level among sickle cell anemia patients — clinical trialView study →}.

A systematic review of 29 clinical trials concluded that ingested gum arabic behaves as a prebiotic and alters biochemical, inflammatory and adiposity markers downstream of that fermentation ^{1Reference 1Al-Jubori et al. · 2023Systematic reviewThe Efficacy of Gum Arabic in Managing Diseases: A Systematic Review of Evidence-Based Clinical Trials — systematic reviewView study →}. The anti-inflammatory and metabolic signals below are thought to follow largely from the butyrate it produces ^{3Reference 3Elnour et al. · 2023ReviewPrebiotic potential of gum Arabic for gut health — reviewView study →}.

Gum arabic, with a mechanistic contribution from catechu. The most consistent human finding for gum arabic is a drop in C-reactive protein.

In a randomized dose-ranging trial, 10–40 g/day for four weeks lowered CRP in chronic-kidney-disease patients even at the lowest dose ^{4Reference 4Elamin et al. · 2017RCTGum Arabic Reduces C-Reactive Protein in Chronic Kidney Disease Patients without Affecting Urea or Indoxyl Sulfate Levels — randomised trialView study →}. A phase II trial in hemodialysis patients (30 g/day, 12 weeks) reduced both CRP and the oxidative marker malondialdehyde while raising total antioxidant capacity ^{5Reference 5Ali et al. · 2020RCTGum Arabic Augmented Total Antioxidant Capacity and Reduced C-Reactive Protein among Haemodialysis Patients in a Phase II Trial — randomised trialView study →}, and a trial in sickle-cell anemia found the same CRP reduction over 12 weeks ^{6Reference 6Kaddam et al. · 2020Clinical trialEffect of Gum Arabic (Acacia senegal) on C-reactive protein level among sickle cell anemia patients — clinical trialView study →}.

The proposed mechanism is butyrate produced by colonic fermentation acting on systemic inflammatory signaling. Separately, the catechu catechin fraction suppresses NF-κB, COX-2 and 5-LOX in stimulated macrophages ^{19Reference 19Altavilla et al. · 2009In vitroFlavocoxid, a dual inhibitor of cyclooxygenase and 5-lipoxygenase, blunts pro-inflammatory phenotype activation in endotoxin-stimulated macrophages — in vitroView study →}. Effects are modest and measured on biomarkers, not clinical endpoints.

Gap: all trials are small and biomarker-based (CRP), with no hard clinical outcomes; the effect is specific to ingested gum arabic, not to bark preparations.

Gum arabic. Two randomized, placebo-controlled trials from the same group report modest anthropometric effects. In 120 healthy women, 30 g/day gum arabic for six weeks reduced BMI by 0.32 and body-fat percentage by 2.2 points versus pectin placebo ^{7Reference 7Babiker et al. · 2012RCTEffects of Gum Arabic ingestion on body mass index and body fat percentage in healthy adult females: randomised, placebo-controlled, double-blind trial — RCTView study →}. In 91 type-2 diabetic patients, 30 g/day for three months lowered the visceral adiposity index by ~24% and systolic blood pressure by ~7.6%, though waist-to-hip ratio was unchanged ^{8Reference 8Babiker et al. · 2018RCTEffect of Gum Arabic (Acacia Senegal) supplementation on visceral adiposity index and blood pressure in patients with type 2 diabetes mellitus — randomised placebo-controlled trialView study →}.

A broader systematic review of fiber supplements judged gum arabic’s weight effect real but small, and “not considerable” in clinical terms without accompanying dietary change ^{9Reference 9Namazi et al. · 2018Systematic reviewAre Isolated and Complex Fiber Supplements Good Choices for Weight Management? A Systematic Review — systematic reviewView study →}.

Gap: the positive trials share a research group and rely on the viscous-fiber satiety mechanism common to all soluble fibers; independent replication and larger samples are lacking.

Black wattle bark in vitro; gum arabic in humans. Condensed tannins and flavan-3-ols from Acacia mearnsii bark are potent radical scavengers, which is what led to the wattle-tannin supplement ^{23Reference 23Ogawa et al. · 2018In vitroTannins from Acacia mearnsii De WildView study →}. In vivo, gum arabic reduced oxidative and nitrosative stress markers in the gut of CKD mice ^{11Reference 11Ali et al. · 2020AnimalGum arabic reduces inflammation, oxidative and nitrosative stress in the gastrointestinal tract of mice with chronic kidney disease — mouse, in vivoView study →}, and in humans the hemodialysis trial showed a significant rise in total antioxidant capacity with 30 g/day ^{5Reference 5Ali et al. · 2020RCTGum Arabic Augmented Total Antioxidant Capacity and Reduced C-Reactive Protein among Haemodialysis Patients in a Phase II Trial — randomised trialView study →}.

The likely contributors on the bark side are the polyphenols — gallic acid, ellagic acid and the flavonols quercetin and kaempferol — rather than the gum polysaccharide itself.

Gap: the strongest antioxidant data are in vitro on wattle bark tannins, while the human data are for the gum. The human antioxidant effect is not attributable to the bark polyphenols, because the participants were not taking them.

Gum arabic, with the oldest signal from babul. A double-blind RCT (n=60) found that gum arabic powder applied twice daily, after scaling, significantly reduced plaque and gingival index scores and gingival-crevicular IL-1β over 60 days versus cellulose placebo ^{14Reference 14Gafar et al. · 2022RCTEffect of Gum Arabic on plaque-induced gingivitis: A randomised controlled trial — RCTView study →}.

A systematic review of medicated chewing gums lists acacia among ingredients with a positive effect on plaque scores, though it rates the overall evidence weaker than for chlorhexidine ^{15Reference 15Keukenmeester et al. · 2014Systematic reviewThe effect of medicated, sugar-free chewing gum on plaque and clinical parameters of gingival inflammation: a systematic review — systematic reviewView study →}. The earliest signal is a 1991 blind crossover of Acacia arabica chewing gum — babul, under its old name — that found lower plaque deposition than sugar-free gum ^{16Reference 16Gazi · 1991RCTThe finding of antiplaque features in Acacia Arabica type of chewing gum — randomised crossover clinical trialView study →}.

Gum arabic. Randomized trials in CKD and hemodialysis patients consistently lower inflammatory markers (CRP) but show no effect on serum urea or creatinine ^{4Reference 4Elamin et al. · 2017RCTGum Arabic Reduces C-Reactive Protein in Chronic Kidney Disease Patients without Affecting Urea or Indoxyl Sulfate Levels — randomised trialView study →}, and one trial recorded a small drop in serum sodium ^{4Reference 4Elamin et al. · 2017RCTGum Arabic Reduces C-Reactive Protein in Chronic Kidney Disease Patients without Affecting Urea or Indoxyl Sulfate Levels — randomised trialView study →}.

The nephroprotective findings are stronger in animals: gum arabic markedly attenuated renal dysfunction and glomerular/tubular lesions in adenine-induced chronic renal failure in rats ^{10Reference 10Ali et al. · 2010AnimalEffects of Gum Arabic in rats with adenine-induced chronic renal failure — animal model, in vivoView study →} and reduced gut inflammation in CKD mice ^{11Reference 11Ali et al. · 2020AnimalGum arabic reduces inflammation, oxidative and nitrosative stress in the gastrointestinal tract of mice with chronic kidney disease — mouse, in vivoView study →}. A 2024 narrative review attributes these effects to its antioxidant and anti-inflammatory actions ^{12Reference 12Alobaidi · 2024ReviewTherapeutic Potential of Gum Arabic (Acacia senegal) in Chronic Kidney Disease Management: A Narrative Review — reviewView study →}.

Gap: human trials have not shown an improvement in kidney function — urea and creatinine were unchanged, and the measured benefit was anti-inflammatory.

Catechu (Senegalia catechu), in a combination product. Catechu bark and heartwood are the source of the catechin half of flavocoxid (marketed as Limbrel), combined with Scutellaria baicalensis baicalin.

A randomized controlled trial (n=79) of the UP446 blend versus naproxen over one week found significant reductions in knee pain and stiffness and improved range of motion ^{17Reference 17Arjmandi et al. · 2014RCTA combination of Scutellaria baicalensis and Acacia catechu extracts for short-term symptomatic relief of joint discomfort associated with osteoarthritis of the knee — randomised controlled trialView study →}, and a 12-week safety RCT found it well tolerated ^{20Reference 20Morgan et al. · 2009RCTThe safety of flavocoxid, a medical food, in the dietary management of knee osteoarthritis — randomised trialView study →}. The mechanism is dual COX/5-LOX inhibition demonstrated in macrophages ^{18,19Reference 18Bitto et al. · 2014ReviewFlavocoxid, a nutraceutical approach to blunt inflammatory conditions — reviewView study →Reference 19Altavilla et al. · 2009In vitroFlavocoxid, a dual inhibitor of cyclooxygenase and 5-lipoxygenase, blunts pro-inflammatory phenotype activation in endotoxin-stimulated macrophages — in vitroView study →}.

The product is a combination, so the effect cannot be attributed to catechu alone, and flavocoxid carries a documented idiosyncratic liver-injury signal ^{21Reference 21Chalasani et al. · 2012ObservationalAcute liver injury due to flavocoxid (Limbrel), a medical food for osteoarthritis: a case series — observational case seriesView study →}.

Gap: no trial isolates catechu from the Scutellaria co-ingredient, and the liver-injury case series followed the efficacy trials.

Gum arabic in animals, black wattle in vitro. In alloxan-induced diabetic rats, gum arabic lowered serum glucose, raised insulin and improved pancreatic islet structure over 21 days ^{13Reference 13Ibrahim et al. · 2023AnimalArabic gum ameliorates systemic modulation in Alloxan monohydrate-induced diabetic rats — rat, in vivoView study →}.

Catechin-rich polyphenol fractions from Acacia mearnsii bark inhibit the carbohydrate-digesting enzymes α-glucosidase and α-amylase in vitro ^{22Reference 22Xiong et al. · 2017In vitroPolyphenols isolated from Acacia mearnsii bark with anti-inflammatory and carbolytic enzyme inhibitory activities — in vitroView study →}. The visceral-adiposity trial was run in type-2 diabetics but measured adiposity and blood pressure, not glycemic control ^{8Reference 8Babiker et al. · 2018RCTEffect of Gum Arabic (Acacia Senegal) supplementation on visceral adiposity index and blood pressure in patients with type 2 diabetes mellitus — randomised placebo-controlled trialView study →}.

Gap: no human trial has measured fasting glucose or HbA1c as a primary outcome, and the two strands of evidence come from different plants.

Babul (Vachellia nilotica). Tannin-rich extracts inhibit bacteria in vitro. Ethanolic leaf extract inhibited the periodontal pathogens Fusobacterium nucleatum and Porphyromonas gingivalis ^{26Reference 26Chandra Shekar et al. · 2018In vitroAntimicrobial Efficacy of Acacia nilotica, Murraya koenigii, Eucalyptus hybrid, Psidium guajava extracts on Fusobacterium nucleatum and Porphyromonas gingivalis — in vitroView study →}, and earlier work documented antibacterial activity against a range of organisms ^{27Reference 27Abd el Nabi et al. · 1992In vitroAntimicrobial activity of Acacia nilotica (L.) Willd. ex Del. var. nilotica — in vitroView study →}. The activity tracks the condensed-tannin and gallic acid content, which precipitates microbial proteins.

Catechu, one cell line. An ethanolic Senegalia catechu seed extract triggered apoptosis in SCC-25 human oral squamous carcinoma cells at 25–50 µg/mL, upregulating caspase-8/9, Bax and cytochrome c while downregulating Bcl-2 ^{25Reference 25Lakshmi et al. · 2017In vitroAcacia catechu Ethanolic Seed Extract Triggers Apoptosis of SCC-25 Cells — in vitroView study →}. No study has tested this in a living animal.

Gum arabic. Gum arabic (Senegalia senegal, Vachellia seyal) is a well-tolerated dietary fibre and an approved food additive. The main adverse effects reported in trials were transient first-week bloating, nausea and mild diarrhoea at 30 g/day ^{7Reference 7Babiker et al. · 2012RCTEffects of Gum Arabic ingestion on body mass index and body fat percentage in healthy adult females: randomised, placebo-controlled, double-blind trial — RCTView study →}.

Tannin-rich barks. Catechu, babul and black wattle are astringent and can irritate the digestive tract or add to constipation with heavy use. Like other high-tannin herbs they can reduce the absorption of iron and other minerals, and bind alkaloid or protein drugs in the gut. Bark preparations are used in short courses.

Catechu and flavocoxid. The flavocoxid combination product (catechu catechins plus Scutellaria baicalin, marketed as Limbrel) caused clinically significant, reversible drug-induced liver injury in a documented case series ^{21Reference 21Chalasani et al. · 2012ObservationalAcute liver injury due to flavocoxid (Limbrel), a medical food for osteoarthritis: a case series — observational case seriesView study →}. The traditional record does not link liver injury to catechu heartwood itself.

The alkaloid wattles. Tyramine-containing species could interact with MAOI antidepressants, since dietary tyramine combined with MAO inhibition can raise blood pressure sharply. Several Australian species also carry tryptamine alkaloids in the root bark. These properties belong to particular species, which is why unidentified acacia bark, root bark, seeds or foliage are not taken internally.

Interactions. No systematic drug-interaction study of gum arabic or acacia bark exists. The tyramine–MAOI concern is theoretical, and the one documented signal is the flavocoxid liver injury.