Keywords

FormalPara Vernaculars:

Urd.: Aqaqia , Babool , Samagh-e-Arabi ; Hin. : Babool , Keekar , Kikar ; San. : Babbūla , Barbūra , Kala-babal , Kinkirāta , Mālāphala , Pitapuspa , Sūksmapatra , Vabbula , Yugmakanta ; Ben. : Babala , Babla (Bāblā ), Babool ; Mal. : Babola , Babul , Kalababli , Karivelam , Karuvelum ; Mar.: Babhul , Babli , Tamra-gond , Vedibabul ; Tam.: Karu-vael , Karuve (karuvē ), Karuvel , Karuvelam , Karuvelamaram ; Tel.: Barbaramu , Barburamu , Nalla-umona , Nallatumma , Thumma chettu , Tumma , Tumma bamka ; Ara.: Akasia alnil , Al samgh al’ arabi (gum), Aqaqia (extract), Mughilan , Sunt , Umm-e-gheelan ; Chi.: 阿拉伯金合欢, A la bo jin he huan , Jiao shu , Tsung ; Dut.: Babul , Echte acacia , Gom-acacia ; Eng.: Acacia gum , Gum Arabica , Gum Senegal ; Fre.: Acacia à gomme , Acacia du Nil , Acacia du Sénégal , Acacia nilotique , Gommier rouge ; Ger.: Ägyptische Akazie , Ägyptischer Schotendorn , Arabische Gummiakazie ; Gre.: Akakia i arabiki ; Ita.: Acacia arabica ; Jap.: Arabia akashia , Arabia gomu modoki ; Per.: Kharo , Kare-mughilan , Mugheelan ; Por.: Acácia-egípcia ; Rus. : Akatsiia arabiiskaia , Akatsiia nilotika , Akatsiia nil’skaia ; Sen.: Red gum ; Sin.: Baabulu , Katu kihiri ; Spa.: Acacia arábiga , Acacia de Egipto , Acacia gomifera , Espino egipcio Swe.: Bablah , Gummiakacia ; Tag.: Sibuyas .

FormalPara Description:

A tropical shrub or flat-topped tree, found throughout tropical Africa, India, Iraq, and West Indies; up to 9 m high but usually less than 4.5 m with short trunk, and pale, fissured and flaking bark. A translucent gum accumulates in the cambium and exudes from cracks or wounds in the bark. The flexuous branches bear sharp thorns 7 mm long, grouped in 3s on the enlarged nodes; the central thorn being slightly recurved. Leaves are deciduous, bi-pinnately compound. Flower buds and flowers are bright golden-yellow in color, solitary or in 2s or 3s, usually emerging before the new leaves, that are ivory white in dense spikes. Fruit is a flat, papery seed pod, brown, pubescent, oblong, 20 to 25 mm wide and 4 to 12.5 mm long, containing 1 to 6 greenish-brown, disk-like seeds. Pods do not split open. The tree is said to produce seeds at five years intervals.III,XXIX,XXXII,XLI

Gum exudate from the bark hardens on exposure to air into globular or angular ‘tears’, up to 4 cm wide, white, yellowish or pinkish in color. Gum from wild trees is usually darker than that from cultivated trees. It is very brittle, nearly scentless and bland in taste; soluble in water and insoluble in alcohol,IV,C ether and oils.CXI Gum Arabica is a branched chain complex polysaccharide, primarily indigestible in humans, and extensively used as food additive [7, 42]. Most of the gum Arabica used commercially comes from A. senegal and various pharmacological studies reported here were carried out on gum Arabica obtained from this source (Figs. 1, 2 and 3).

Fig. 1
figure 1

Acacia nilotica, Tree in Bloom, J.M. Garg, WikimediaCommons; ShareAlike 3.0 Unported CC BY-SA 3.0, https://commons.wikimedia.org/wiki/File:Babool_(Acacia_nilotica)_flowers_at_Hodal_W_IMG_1248.jpg; https://creativecommons.org/licenses/by-sa/3.0/deed.en

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Fig. 2
figure 2

Acacia nilotica, Flowers, J.M. Garg, WikimediaCommons; ShareAlike 3.0 Unported CC BY-SA 3.0, https://commons.wikimedia.org/wiki/Category:Acacia_nilotica#/media/File:Babool_(Acacia_nilotica)_flowers_at_Hodal_W_IMG_1163.jpg; https://creativecommons.org/licenses/bysa/3.0/deed.en

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Fig. 3
figure 3

Acacia nilotica, Gum, Prof. Akbar, Original

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FormalPara Actions and Uses:

Gum acacia has been used for centuries in traditional medicines. Egyptians and other Arab physicians used it extensively to treat a wide variety of ailments and therefore it is also known as Samagh-e-Arabi . It is still an important constituent of many pharmaceutical products of the traditional medicines of various developing countries. However, the modern uses of gum acacia in pharmaceutical industry are confined to as a demulcent in cough mixtures and as stabilizer in emulsions. The bark of this and several other Acacia species is used in India to prepare spirit from sugar and palm juice by precipitating the albuminous substances in the liquor and facilitating fermentation.XL Ibn al-BaitarLXIX mentioned that this tree is mainly found in Hijaz region of Arabia, and referring to Avicenna says, it is beneficial in bleeding. In Unani medicine, the leaves, flowers, legumes, and bark are regarded cold 2° and dry 2° in temperament, while the gum is considered moderate; the gum is ascribed astringent, demulcent, emollient, antiseptic, tonic and nutritive properties, and is used for irritated conditions of mucous membranes, such as cough, sore throat, chronic bronchitis, diarrhea, dysentery, leucorrhea, cystitis, urethritis, gonorrhea, burns, sore nipples, inflammations and nodular leprosy.L Pounded tender leaves into a pulp are administered in dysentery and diarrhea; the leaves decoction used as gargle is useful in spongy gums and relaxed sore throat, and to wash hemorrhagic ulcers and wounds.CV Decoction of leaves and pods is dried and made into tablets, and is known as Aqaqia . It is astringent and styptic, and is used for leucorrhea, menorrhagia, and to stop bleeding from any organ.LXXVII A paste of the gum with egg white is applied in conjunctivitis. It is also reported to be useful as food for diabetic patients.LXXXI The bark is astringent, demulcent, refrigerant and antiseptic,XXI,LXXVII and its decoction is used as gargle and mouth wash in sore throat, foul aphthous stomatitis, cancerous and syphilitic affections, for copious salivation,XXI,LXXXI,CV as a douche in leucorrhea and vaginal discharges, as an enema in piles and prolapse of rectum,XXI and to wash ulcers.LXXXI The burnt wood is used as antacid, and the gum increases viscosity of seminal fluid; however, it is said to sclerose blood vessels.CXXXXVII British Pharmacopoeia describes gum acacia as a source of useful medicaments. It is believed to be of value in treating gingivitis and reducing plaque [28]. Several species of acacia are also used as chewing sticks and are credited with antibacterial effect on oral bacteria. In East Africa, the bark decoction is used to treat diarrhea and stomach disorders, while the root decoction is mildly purgative and is given in cases of constipation, stomachache and for the treatment of gonorrhea. Powdered bark with ginger oil is used externally for cancerous afflictions. Pods are used in cough; leaves are local stimulant and poultices of bruised tender leaves are applied to wounds with foul discharges.LXXXV In Livingstone, a southern Province of Zambia, the plant was utilized to treat HIV/AIDS-related infections during the epidemic [21].

Chief use of the gum in pharmacy is as an emulsifying agent to suspend insoluble powders in aqueous mixtures, and as a binding agent to make pills and tablets specially cough drops and lozenges. It is commonly employed as a demulcent in preparations designed to treat diarrhea, dysentery, coughs, sore throat and fevers.CLIV

FormalPara Phytoconstituents:

The gum is chiefly composed of calcium, magnesium and potassium salts of polysaccharides, and is built upon a backbone of d-galactose units with side chains of d-glucuronic acid with l-rhamnose or l-arabinose as terminal units. On hydrolysis with dilute acid, it yields 1-arabinose, 1-rhamnose and 3-d-galactoside-1-arabinose. The residue consists of galactose and uronic acid [14, 16],XXIV When hydrolyzed with dilute sulphuric acid, it yields 1-rhamnopyranose, d-galactopyranose, 1-arabofuranose and aldobionic acid 6-d-glucuronosido-d-galactose.C,CXXXXI It possesses an oxidase-type enzyme which is destroyed by heating at 100 °C, and 12–15% of water.XXIV Presence of cardiac glycosides and flavonoids has been reported in Acacia arabica leaves [50].

FormalPara Pharmacology:

Gentamicin-induced nephrotoxicity in rats was significantly ameliorated by pretreatment and concomitant treatment with gum Arabic, in part, due to reduced oxidative stress [10]. However, Ali et al. [5] reported a modest protection against gentamicin-nephrotoxicity. Administration of gum Arabic to healthy rats for eight days also did not significantly affect the levels of free radical scavengers, such as GSH, ascorbic acid, and SOD in kidneys and the liver [8]. Ali et al. [4] also reported that gum Arabic treatment of rats for 5-weeks, following a two-stage surgical nephrectomy to induce chronic renal failure (CRF), slightly and insignificantly reduced the CRF-induced increases in urea and creatinine concentrations. Also, gum Arabic co-treatment with cisplatin did not prevent cisplatin-nephrotoxicity, though the cisplatin-induced LPO was significantly reduced by gum Arabic treatment [9]. Gum Arabic treatment significantly but incompletely reversed adenine-induced increase in plasma creatinine, urea, and urinary protein; and increased SOD activity and GSH concentration in renal homogenate [6]. Gum Arabic administration to normal mice significantly increased creatinine renal clearance and antidiuretic hormone, and decreased daily sodium and urinary output [38]. Pretreatment of mice with gum Arabic significantly protected against APAP-hepatotoxicity without affecting APAP-induced glutathione depletion but significantly reducing LPO and NO formation [27]. Doxorubicin-cardiotoxicity is also significantly prevented by treatment with gum Arabic [1].

Wadood et al. [55] reported significant hypoglycemic effect of powdered seeds in normal rabbits, but no significant effect on blood glucose of alloxan-diabetic rabbits. Chloroform extract of Acacia bark significantly decreased blood glucose of alloxan-diabetic rats and reversed values of TC, LDL-C, HDL-C and TGs [41]. Similar results of chloroform bark extract in alloxan-diabetic rats were reported after 21-days of treatment. There were significant decreases in serum levels of glucose, TC, LDL-C, TGs and MDA, while serum insulin and HDL-C were significantly increased, compared to control diabetic animals [30]. Gum Arabic, however, did not lower serum cholesterol in rats [53], it decreased cholesterol absorption and increased its biosynthesis in cholesterol-fed rats [32]. Inhibition of LDL-C oxidation [17], and uncoupling of oxidative phosphorylation in liver and heart mitochondria, and partial inhibition of mixed function oxidases of liver endoplasmic reticulum by gum Arabica have also been reported [19]. Addition of gum Arabic to oral rehydrating solution increases water and electrolytes absorption in normal and chronic osmosecretory diarrhea model in rats [23, 56], enhances recovery from diarrhea [52], reduces cholera toxin-induced sodium excretion [54], and decreases nitrite and nitrate formation in jejunum [45]. Sethi et al. [49] reported an insignificant (11%) abortifacient activity of aqueous flowers extract in rats, that also caused a 50 and 7.5% decrease in fetal body weight and length, respectively. However, the same administered orally to rats for 10-days after insemination was found ineffective as abortifacient [39].

Whole gum fine aqueous suspension inhibited growth of fresh isolates and reference strains of P. gingivalis and P. intermedia cultures; while a soluble fraction of aqueous suspension showed no similar activity [22]. Methanol leaf extract is moderately active against S. aureus, S. typhi, S. paratyphi, and S. flexineri [50]. Antibacterial activity of water extract of chewing sticks against S. fecalis was reported by Almas [11]. Gum Arabic has also been reported to enhance remineralization of caries-like enamel lesions of teeth in vitro, similar to sodium fluoride, suggesting a preventing effect against caries [40].

FormalPara Clinical Studies:

Gum Arabic is reported useful in cases of chronic renal disease, especially the End-Stage Renal Disease (ESRD) requiring renal replacement therapy (dialysis). Two out of three children with ESRD treated with gum acacia (1 g/kg/day in divided doses) as complementary to low-protein diet reported improvement in well-being and reduction in serum creatinine and urea levels not achieved previously without dialysis [12]. An 11-years old girl with ESRD, who required peritoneal dialysis to control uremic symptoms despite conservative measures, was treated with gum acacia along with other conservative measures, after the parents refused further dialysis treatment. The patient continuously improved over time and never experienced acidotic or significant uremic symptoms over a four-year dialysis-free period [13]. Another case of ESRD treated with gum Arabic remained dialysis-free for six-years with improved well-being and without uremia [2]. Beneficial effects of gum Arabic on serum creatinine, urea and uric acid were also observed in 36 chronic renal failure patients who required regular hemodialysis, and in 10 normal healthy subjects. Supplementation of low protein diet with gum Arabic in a dose of 50 g/day for 3 months significantly reduced serum urea levels by 31%, and the decrease was even greater (44%) in patients who were also given ferrous sulfate (200 mg/day) and folic acid (5 mg/day), compared to their baseline values. Serum creatinine was decreased by 9.9 and 12.6% in these groups, respectively, and by 11.7% in normal volunteers, compared to patients that were treated with only iron and folic acid [3]. An 8-weeks study in seven normal healthy volunteers, administered 25 g/day of gum acacia, showed increased serum butyrate levels by two-fold. Exposure of renal epithelial cells to increased levels of butyrate suppressed both basal and stimulated generation of the profibrotic cytokine transforming growth factor-beta1 [36].

Ross [46] reported no significant effect of 3-weeks administration of gum Arabic on glucose tolerance in healthy men, but serum cholesterol was decreased. Since no gum was recovered from the stools, it was suggested that it was metabolized in the colon. Mee and Gee [37] also reported a decrease in TC and LDL-C in men with mild hypercholesterolemia. However, administration of water-soluble dietary fiber from gum acacia (15 g/d) for 4 to 12-weeks to hypercholesterolemic men and women failed to lower TC, LDL-C, VLDL-C and TGs or to increase HDL-C in double-blind controlled studies [29, 31]. Calame et al. [20] found gum Arabic producing prebiotic effect, increasing the useful Bifidobacteria and Lactobacilli in healthy human volunteers, with 10 g being the optimal daily dose. Gazi [28] reported antiplaque activity of Acacia gum compared to sugar-free gum in two blind crossover clinical trials. RCTs have also indicated usefulness of commercially available gel [43, 44] and toothpastes [51] containing A. arabica in patients with gingivitis, comparable to chlorhexidine.

FormalPara Human A/Es, Allergy and Toxicity/Safety:

Sensitization to gum Arabic carbohydrates has been reported in atopic patients with pollen sensitization without obvious exposure to it [47]. An unusual case of a teenager with plasma cell gingivitis due to antigenic reaction to toothpaste containing A. arabica was reported [35]. International Food Safety authorities put no limitation on the use of gum Arabic as a food additive, if it is used with established criteria of identity and purity [15]. A report also concluded that extensive safety test data support the safety of A. senegal gum and gum extract, and these two ingredients are safe as used in cosmetic formulations. According to industry data only material from A. senegal are in current use in concentrations ranging from 9% in mascara to 0.0001% in tonics, dressings and other hair grooming aids [18]. In Unani medicine, it is considered harmful for GIT.LXXVII

FormalPara Animal Toxicity:

No dose-related changes in maternal findings, number of fetuses, fetal viability or external, visceral or skeletal abnormalities were noted when gum acacia was given up to 15% in diet ad lib to male and female rats during pre-mating, mating and throughout gestation [24]. A toxicity study (subchronic toxicity) of gum Arabic (from A. senegal) administered orally in diet to F344 rats at doses up to 5% produced no clinical changes, survival, body weight, food and water consumption, changes in urine, hematology or blood chemistry at the end of 90-days treatment [25]. Flowers of A. arabica are also devoid of any teratogenicity [39]. Even modified gum acacia showed no mutagenic potential, and the LD50 in Sprague Dawley rats was determined to be >2,000 mg/kg, while subacute toxicity studies of 13-weeks administration showed no untoward effects or histological findings [48].

FormalPara Potential Drug-Herb Interactions:

Acacia gum may reduce the effectiveness of preservative methyl-p-hydroxybenzoate against P. aeruginosa by its physical barrier protection of microbial cells from the action of the agent [33]. Administration of gum Arabic concurrently or 2 h before amoxicillin is reported to significantly decrease the Cmax of amoxicillin [26], and it can also antagonize phenobarbital-induced demethylation of aminopyrine [34]. Due to the presence of enzymes, it should not be used for preparations with readily oxidizable ingredients e.g. vitamin A, and is also incompatible with drugs containing morphine, apomorphine, eugenol, phenol, thymol, guiacol, cresols, epinephrine, aminopyrine, vanillin, creosol, eserine, isobarbaloin, gallic acid, and tannins; also with strong alcoholic liquids, solutions of ferric chloride and lead subacetate and strong solution of sodium borate.CXI

FormalPara Commentary:

Although dramatic beneficial effects of gum Arabic in ESRD have been reported, they have been reported only from one source, that need to be verified in other patient populations and in RCTs.