Arabinosio: struttura chimica, funzione biologica, fonti, applicazioni e sicurezza

Definizione
L’arabinosio è uno zucchero monosaccaride appartenente alla classe dei pentosi aldoesosi (formula molecolare C₅H₁₀O₅), composto da cinque atomi di carbonio e un gruppo aldeidico. In natura si trova prevalentemente nella forma L-arabinosio, una caratteristica rara, poiché la maggior parte degli zuccheri biologici esiste nella forma D.

L’arabinosio è un componente strutturale importante delle emicellulose vegetali, in particolare di arabinani, arabinoxilani e polisaccaridi pectinici, che formano la parete cellulare delle piante.

1. Proprietà chimiche

• Formula molecolare: C₅H₁₀O₅

• Massa molare: 150,13 g/mol

• Isomeri: L-arabinosio (biologicamente rilevante), D-arabinosio (meno comune)

• Struttura:

  • zucchero a cinque atomi di carbonio con gruppo aldeidico in posizione 1

  • può esistere in forma ciclica (furanosica) o lineare in soluzione acquosa

• Solubilità: altamente solubile in acqua

• Sapore: dolcezza moderata (~50% rispetto al saccarosio)

2. Presenza in natura e fonti

• Componente di polisaccaridi vegetali complessi, in particolare in:

  • gomma arabica

  • pectina

  • emicellulose dei cereali (es. frumento, mais)

  • fibre vegetali (es. polpa di barbabietola, legumi)

• Si libera tramite idrolisi enzimatica o acida dei polisaccaridi vegetali

3. Funzione biologica e metabolismo

• Non rappresenta uno zucchero metabolico primario nell’uomo, ma può essere parzialmente assorbito nell’intestino tenue

• Ha un indice glicemico molto basso

• Agisce come inibitore competitivo della sucrasi, rallentando la digestione del saccarosio → può ridurre l’assorbimento di glucosio

• È fermentabile dalla flora intestinale, producendo acidi grassi a catena corta (SCFA) come acetato, propionato e butirrato

• Potenziale effetto prebiotico, promuove la crescita di batteri benefici (es. Bifidobacterium, Lactobacillus)

4. Applicazioni tecnologiche e industriali

Alimentazione e nutrizione

• Utilizzato in formulazioni a basso indice glicemico

• Impiegato in alimenti funzionali per modulare la risposta glicemica

• Incluso in integratori di fibra solubile

Farmaceutica e biochimica

• Utilizzato in test metabolici e studi sulla digestione dei carboidrati

• Come zucchero non digeribile, impiegato in sistemi di rilascio controllato

• Presente in alcune formulazioni prebiotiche e prodotti per la regolarità intestinale

Ricerca e biotecnologie

• L-arabinosio è un induttore metabolico nel sistema di espressione araBAD in E. coli

• Utilizzato come substrato per la sintesi di intermedi sintetici e derivati della vitamina C

5. Sicurezza e tollerabilità

• Considerato sicuro per il consumo umano

• Presente naturalmente in molti alimenti vegetali

• Non tossico anche a dosi elevate

• Può causare gonfiore o gas se assunto in grandi quantità, per fermentazione intestinale

• Autorizzato in vari paesi per uso alimentare e nutraceutico

6. Conclusione

L’arabinosio è uno zucchero pentoso naturale, con basso impatto glicemico e proprietà prebiotiche, presente in molte fibre vegetali. Ha applicazioni in ambito nutrizionale, farmaceutico e biotecnologico, dove viene sfruttato per la sua funzionalità metabolica e per il ruolo di regolatore nei sistemi genetici microbici.

È un composto versatile, sicuro e naturale, sempre più utilizzato in prodotti orientati alla salute metabolica e all’equilibrio intestinale.

Bibliografia_________________________________________________________________________

Newman PP, Schmitt BL, Maurmann RM, Pence BD. Polysaccharides with Arabinose: Key Players in Reducing Chronic Inflammation and Enhancing Immune Health in Aging. Molecules. 2025 Mar 6;30(5):1178. doi: 10.3390/molecules30051178.

Abstract. Aging is associated with a decline in physiological performance leading to increased inflammation and impaired immune function. Polysaccharides (PLs) found in plants, fruits, and fungi are emerging as potential targets for therapeutic intervention, but little is known about their effects on chronic inflammation and aging. This review aims to highlight the current advances related to the use of PLs, with the presence of arabinose, to attenuate oxidative stress and chronic and acute inflammation, and their immunomodulatory effects associated with antioxidant status in monocytes, macrophages, and neutrophil infiltration, and leukocyte rolling adhesion in neutrophils. In addition, recent studies have shown the importance of investigating the 'major' monosaccharide, such as arabinose, present in several of these polysaccharides, and with described effects on gut microbiome, glucose, inflammation, allergy, cancer cell proliferation, neuromodulation, and metabolic stress. Perspectives and opportunities for further investigation are provided. By promoting a balanced immune response and reducing inflammation, PLs with arabinose or even arabinose per se may alleviate the immune dysregulation and inflammation seen in the elderly, therefore providing a promising strategy to mitigate a variety of diseases.

Pasmans K, Meex RCR, Trommelen J, Senden JMG, Vaughan EE, van Loon LJC, Blaak EE. L-arabinose co-ingestion delays glucose absorption derived from sucrose in healthy men and women: a double-blind, randomised crossover trial. Br J Nutr. 2022 Sep 28;128(6):1072-1081. doi: 10.1017/S0007114521004153.

Abstract. Dietary interventions to delay carbohydrate digestion or absorption can effectively prevent hyperglycaemia in the early postprandial phase. L-arabinose can specifically inhibit sucrase. It remains to be assessed whether co-ingestion of L-arabinose with sucrose delays sucrose digestion, attenuates subsequent glucose absorption and impacts hepatic glucose output. In this double-blind, randomised crossover study, we assessed blood glucose kinetics following ingestion of a 200-ml drink containing 50 g of sucrose with 7·5 g of L-arabinose (L-ARA) or without L-arabinose (CONT) in twelve young, healthy participants (24 ± 1 years; BMI: 22·2 ± 0·5 kg/m2). Plasma glucose kinetics were determined by a dual stable isotope methodology involving ingestion of (U-13C6)-glucose-enriched sucrose, and continuous intravenous infusion of (6,6-2H2)-glucose. Peak glucose concentrations reached 8·18 ± 0·29 mmol/l for CONT 30 min after ingestion. In contrast, the postprandial rise in plasma glucose was attenuated for L-ARA, because peak glucose concentrations reached 6·62 ± 0·18 mmol/l only 60 min after ingestion. The rate of exogenous glucose appearance for L-ARA was 67 and 57 % lower compared with CONT at t = 15 min and 30 min, respectively, whereas it was 214 % higher at t = 150 min, indicating a more stable absorption of exogenous glucose for L-ARA compared with CONT. Total glucose disappearance during the first hour was lower for L-ARA compared with CONT (11 ± 1 v. 17 ± 1 g, P < 0·0001). Endogenous glucose production was not differentially affected at any time point (P = 0·27). Co-ingestion of L-arabinose with sucrose delays sucrose digestion, resulting in a slower absorption of sucrose-derived glucose without causing adverse effects in young, healthy adults.

Kaluzhny DN, Tatarskiy VV Jr, Dezhenkova LG, Plikhtyak IL, Miniker TD, Shchyolkina AK, Strel'tsov SA, Chilov GG, Novikov FN, Kubasova IY, Smirnova ZS, Mel'nik SY, Livshits MA, Borisova OF, Shtil AA. Novel antitumor L-arabinose derivative of indolocarbazole with high affinity to DNA. ChemMedChem. 2009 Oct;4(10):1641-8. doi: 10.1002/cmdc.200900227.

Abstract. Novel indolocarbazole derivative 12-(alpha-L-arabinopyranosyl)indolo[2,3-alpha]pyrrolo[3,4-c]carbazole-5,7-dione (AIC) demonstrated high potency (at submicromolar concentrations) against the NCI panel of human tumor cell lines and transplanted tumors in vivo. In search of tentative targets for AIC, we found that the drug formed high affinity intercalative complexes with d(AT)(20), d(GC)(20) and calf thymus DNA (binding constants (1.6x10(6)) M(-1)< or =K(a)< or =(3.3x10(6)) M(-1)). The drug intercalated preferentially into GC pairs of the duplex. Importantly, the concentrations at which AIC formed the intercalative complexes with DNA (C< or =1 microM) were identical to the concentrations that triggered p53-dependent gene reporter transactivation, the replication block, the inhibition of topoisomerase I-mediated DNA relaxation and death of HCT116 human colon carcinoma cells. We conclude that the formation of high affinity intercalative complexes with DNA is an important factor for anticancer efficacy of AIC.

Zhao L, Wang Y, Zhang G, Zhang T, Lou J, Liu J. L-Arabinose Elicits Gut-Derived Hydrogen Production and Ameliorates Metabolic Syndrome in C57BL/6J Mice on High-Fat-Diet. Nutrients. 2019 Dec 13;11(12):3054. doi: 10.3390/nu11123054. 

Abstract. Obesity and metabolic syndrome (MS) associated with excess calorie intake has become a great public health concern worldwide. L-arabinose, a naturally occurring plant pentose, has a promising future as a novel food ingredient with benefits in MS; yet the mechanisms remain to be further elucidated. Gut microbiota is recently recognized to play key roles in MS. Molecular hydrogen, an emerging medical gas with reported benefits in MS, can be produced and utilized by gut microbes. Here we show oral L-arabinose elicited immediate and robust release of hydrogen in mice in a dose-and-time-dependent manner while alleviating high-fat-diet (HFD) induced MS including increased body weight especially fat weight, impaired insulin sensitivity, liver steatosis, dyslipidemia and elevated inflammatory cytokines. Moreover, L-arabinose modulated gene-expressions involved in lipid metabolism and mitochondrial function in key metabolic tissues. Antibiotics treatment abolished L-arabinose-elicited hydrogen production independent of diet type, confirming gut microbes as the source of hydrogen. q-PCR of fecal 16S rDNA revealed modulation of relative abundances of hydrogen-producing and hydrogen-consuming gut microbes as well as probiotics by HFD and L-arabinose. Our data uncovered modulating gut microbiota and hydrogen yield, expression of genes governing lipid metabolism and mitochondrial function in metabolic tissues is underlying L-arabinose's benefits in MS.

Higaki S, Matsuo T. Toxicity of d-Arabinose in Male and Female Rats. Shokuhin Eiseigaku Zasshi. 2018;59(3):114-120. Japanese. doi: 10.3358/shokueishi.59.114.

Abstract. In order to investigate the feasibility of using the rare sugar d-arabinose as a functional food material, we examined its toxicity in rats. In an acute toxicity study, the lethal dose (LD50) was calculated to be 12.1 g/kg in males and 11.6 g/kg in females. On the other hand, in a short-term toxicity test, rats developed diarrhea when given feed containing 5% d-arabinose, which was the minimum amount added, so the maximum nontoxic amount was estimated to be less than 5%. Thus, the toxicity of d-arabinose is stronger than that of another rare sugar, d-psicose, which was reported to show no toxicity when added at 10% in the diet. Further studies are needed to establish whether d-arabinose would be safe for use as a functional ingredient.

Pueyo C, Lopez-Barea J. The L-arabinose-resistance test with Salmonella typhimurium strain SV3 selects forward mutations at several ara genes. Mutat Res. 1979 Aug;64(4):249-58. doi: 10.1016/0165-1161(79)90094-3. 

Abstract. A new assay has been described for mutagenicity testing using an L-arabinose-sensitive strain of Salmonella typhimurium. The test strain SV3 and several L-arabinose-resistant mutants selected therefrom are characterized in the present study by 3 different criteria: inhibition of growth by L-arabinose, accumulation of keto-sugars, and activities of the enzymes involved in L-arabinose catabolism. Strain SV3 (ara-531) shows high levels of inducible L-arabinose isomerase (EC 5.3.1.4) and L-ribulokinase (EC 2.7.1.16) activities, but is deficient in L-ribulose-5-phosphate 4-epimerase (EC 5.1.3.4), the enzyme encoded in Escherichia coli by gene D in the araBAD operon. Addition of L-arabinose to SV3 growing in glycerol or casamino acids stops growth. D-Glucose only partially reverses this inhibition. Reversion of the ara-531 mutation restores different levels of epimerase activity and resistance to L-arabinose. However, the great majority of the L-arabinose-resistant mutants do not utilize L-arabinose. The physiological and enzymatic properties of these L-arabinose non-utilizing mutants suggest that L-arabinose resistance is due to forward mutations in at least 3 other genes, araA, araB and araC, blocking steps prior to L-ribulose 5-phosphate accumulation.

Irr J, Englesberg E. Control of expression of the L-arabinose operon in temperature-sensitive mutants of gene araC in Escherichia coli B-r. J Bacteriol. 1971 Jan;105(1):136-41. doi: 10.1128/jb.105.1.136-141.1971.

Abstract. Expression of the l-arabinose operon in Escherichia coli B/r is dependent on the temperature of growth of the araC mutants reported in this paper. Analysis of these temperature-sensitive regulatory mutants indicates that both repressor and activator activities are thermolabile. The simplest model to explain the manner in which the operon is controlled is one suggesting that the regulatory gene, araC, codes for a protein which upon synthesis acts as a repressor molecule and prevents operon function. When inducer is added, the repressor undergoes a conformational shift and becomes an activator which switches on enzyme synthesis, provided the repressor concentration is reduced to a sufficiently low level in the cell. These data lend strong support to the model that both activities are the result of the same gene product.