Food nutrient value of fresh leaves per 100 g edible portion reported is moisture 78.1 g, energy 69 kcal, protein 5.0 g, fat 0.7 g, carbohydrate 10.6 g, fibre 3.0 g, ash 2.6 g, Ca 639.1 mg, Fe 4.1 mg and P 109 mg (National Institute of Nutrition-University of Central Florida Project 2001–2004).

Erythaline and erythratine were isolated (Folkers and Koniuszy 1940). Leaves were reported to have a total alkaloidal content of 0.11 % constituting alkaloids erysotrine, erysodine, erysovine, erythaline, erysopine, erysopitine, erysonine, erysodienone, orientaline, hypaphorine, hypaphorine methyl ester and also N,N-dimethyltryptophan (Ghosal et al. 1970, 1972). From the leaves were isolated two alkaloids (erysothrine and hypaphorine) (Nguyen et al. 1991); two tetrahydroprotoberberine alkaloids (scoulerine and (+)-coreximine); a benzyltetrahydroisoquinoline alkaloid (L-reticuline); a dibenz[d, f]azonine alkaloid (erybidine); O-methylerybidine and N-norreticuline (Ito et al. 1973); scoulerine and coreximine (Ito 1999); 10,11-dioxoerythratidine (Herlina et al. 2005); phytol (Herlina et al. 2006); isolate 11 characterized as a triterpene pentacyclic 3b-11a-28-trihydroxy-oleane-2-ene and isolate 17 as a mixture of β-sitosterol and stigmasterol (Herlina et al. 2008); pentacyclic triterpenoid (3,22,23-trihydroxy-oleane-12-ene); pentacyclic triterpenoid (3b,11a-28trihydroxy-oleane-12-ene); and 10,11-dioxoerythratidine (Supratman et al.2010). Kalachaveedu et al. (2011) extracted β-sitosterol (433 mg, 1.445 w/w), oleanolic acid (65 mg, 0.217 % w/w) and β-sitosterol glycoside (108 mg, 0.36 % w/w).

The leaf was found to contain a lectin with molecular weight of 58 kDa, made up of two subunit molecular weights of 30 and 33 kDa (Konozy et al. 2002). The leaf lectin was found to be a glycoprotein with a neutral sugar content of 9.5 %. The leaf lectin was rich in acidic as well as hydrophobic amino acids and totally lacked cysteine and methionine. The N-terminal amino acids were Val-Glu-Thr-IIe-Ser-Phe-Ser-Phe-Ser-Glu-Phe-Glu-Ala-Gly-Asn-Asp-X-Leu-Thr-Gln-Glu-Gly-Ala-Ala-Leu-.

The alkaloid, erythratine, elucidated as 11-hydroxyerysotrine, was isolated from the flowers in Egypt (El-Olemy et al. 1978). The flowers were found to contain 7-methoxy 8-(15-OH pentadecyl)-coumarin; phaseollin; 29-norcycloartenol; 3-β-acetoxy- β-norcholest-5-ene; docosanoic and capric acid; flavonoid abyssinone; prenylated isoflavonoids stigmoidins A, B and C, besides isoquinoline alkaloids erythritol; and isoquinoline alkaloid isococcoline, isoflavones alpinumisoflavone, erythrinin A,B and C, osajin and erythrabasin I (Sharma and Chawla 1992; Chawla and Sharma 1993). Two isoquinoline alkaloids designated erythrosotidienone and erythromotidienone plus stigmasterol, cycloartenol and erysotramidine were isolated from the acetone flower extract (Sharma and Chawla 1998).

Marañon and Santos (1932) found an alkaloid, a fatty oil, and a saponaceous glucoside from the seeds. The alkaloid isolated had the properties identical with those of hypaphorine. From seeds erythraline and ‘free’ and ‘liberated’ erysovine were isolated (Singh and Chawla 1970). The fatty acid composition of the seed oil was also determined. A prenylated flavone glycoside 5,7,4′-trihydroxy-3′-methoxy-8-C-prenylflavone 7-O-β-d-glucopyranosyl-(1 → 3)-α-l-arabinopyranoside (1) was isolated from the seeds (Yadava and Reddy 1999). Nitrogen contents of E. variegata seeds and deoiled seeds showed good protein content; albumin, globulin, prolamine and glutelin were separated out by fractionation (Samanta and Laskar 2008). Fractionation of protein was done to separate albumin, globulin, prolamine and glutelin. The total protein isolates (TPI) and the fractions isolated contained 17 amino acids, most of which were essential.

A d-galactose-binding glycoprotein lectin was purified from the seeds (Datta and Basu 1981). A mitogenic d-galactosephilic lectin was isolated from seeds (Gilboa-Garber and Mizrahi 1981). Kunitz-type trypsin inhibitors, ETIa and ETIb, and chymotrypsin inhibitor ECI were isolated from the seeds (Kouzuma et al. 1992). The proteins ETIa and ETIb comprised 172 and 176 amino acid residues with molecular weight 19,242 and 19,783, respectively, and shared 112 identical amino acid residues, about 65 % identity. A chymotrypsin inhibitor (ECI) isolated from seeds was found to have 179 amino acid residues with a pyroglutamic acid as the N-terminal residue and has a calculated molecular weight of 19,791 (Kimura et al. 1993). About 60 % of the residues of ECI were identical to those of ETIa and ETIb and the reactive sites, Arg63, in ETIa and ETIb were changed to Leu64 in ECI. A Bowman-Birk family proteinase inhibitor (EBI) isolated from the seeds was found to consist of 61 amino acid residues, the shortest among the Bowman-Birk family inhibitors sequenced to date, and with a molecular weight of 6,689 (Kimura et al. 1994). EBI could be classified as a group II inhibitor, showing the best homology (67 %) to the Bowman-Birk proteinase inhibitor from soybeans. Erythrina variegata chymotrypsin inhibitor (ECI) and chymotrypsin molecules were found to undergo aggregation in the complex-forming buffer simultaneously with a binary complex consisting of one ECI and one chymotrypsin molecule in a soluble form (Kimura et al. 1997). ECI comprised two peptides; the N-terminal peptide, ECI-(1-107)-peptide, containing the primary reactive site retained a slight inhibitory activity, while the C-terminal peptide, ECI-(108-179)-peptide, exhibited no inhibitory activity. It was demonstrated that amino acid residues Gln62 (P3), Phe63 (P2), Leu64 (P1) and Phe67 (P3′) in the primary binding loop of Erythrina variegata chymotrypsin inhibitor (ECI), a member of the Kunitz inhibitor family, were involved in its strong inhibitory activity towards chymotrypsin (Iwanaga et al. 1998). It was further shown that the intramolecular interaction between the primary binding loop and the scaffold of ECI played an important role in the strong inhibitory activity towards chymotrypsin (Iwanaga et al. 1999).

The purified seed isolectins (EVLI, EVLII and EVLIII) isolated from E. variegata, were all specific for galactopyranosides and N-acetylgalactosamine, and their affinities for simple sugars were EVLIII greater than EVLII greater than EVLI (Yamasaki et al. 1992). EVLI and EVLIII were found to be homodimers made up of an A-subunit of molecular mass 36,000 and a B-subunit of molecular mass 33,000, whereas EVLII a heterodimer composed of the A- and B-subunits. They found that there was no structural difference of the sugar chains linked to the two subunits of E. variegata galactose-specific isolectins (Yamaguchi et al. 1993). This together with the results of amino acid sequence comparisons indicated that the difference in molecular mass of these two subunits resulted almost wholly from the difference in the number of oligosaccharides linked to them.

The petroleum ether bark extract was found to compose of wax alcohols and wax acids, alkyl ferulates, alkyl phenolates, stigmasterol, sitosterol, campesterol and citrostadienol/24-methylenelophenol (Singh et al. 1975). The ethanol bark extract yielded chloroform-soluble and water-soluble bases, identified as erysovine and stachydrine, respectively. From the bark were isolated isoflavones (erythrinins A,B, C, osajin; alpinumisoflavone; and oxyresveratrol and dihydrooxyresveratrol) (Deshpande et al. 1977), alkaloids (erysotine, erythratidine, epi-erythratidine and 11-hydroxy-epi-erythratidine) (Chawla et al. 1988), three flavonoid phospholipase A₂ (PLA₂) inhibitors (4′-hydroxy-3′,5′-diprenylisoflavonone (abyssinone V) and 3,9-dihydroxy-2,10-diprenylpterocarp-6a-ene (erycrystagallin) and 4′-hydroxy-6,3′,5′-triprenylisoflavonone) (Hedge et al. 1997), erythrinin B (Kobayahsi et al. 1997), alpinumisoflavone and two prenylated isoflavones (erythrivarones A and B characterized as dihydroalpinumisoflavone and 4′-hydroxy-[6″,6″-dimethyldihydropyrano(2″,3″:5,6)]-[6‴,6‴-dimethyldihy dropyrano(2‴,3‴:7,8)] isoflavone, respectively) (Huang and Yen 1996; 1997) and warangalone (Huang and Tseng 1998). Isoflavonoids, eryvarin A and eryvarin B, were isolated from wood (Tanaka et al. 2000). Two isoflavone derivatives named indicanines D and E together with 11 known compounds including six isoflavones (genistein, wighteone, alpinumisoflavone, dimethylalpinumisoflavone, 8-prenyl erythrinin C and erysenegalensein E), one cinnamate (erythrinassinate B), two pentacyclic triterpenes (oleanolic acid and erythrodiol) and two phytosterols (stigmasterol and its 3-O-β-d-glucopyranoside) were isolated from the stem bark (Nkengfack et al. 2001). Huang and Chiang (2004) isolated the following constituents from the methanol stem bark extract: triterpenoids, namely, lup-20(29)-en-3-one; β-amyrin; olean-12-en-3β, 22β-diol; olean-12-en-3β, 28-diol; 22β, 24-dihvdroxvolean-12-en-3-one; oleanonic acid; oleanolic acid; and olean-12-en-3β, 22β, 24-triol along with warangalone and 6,8-diprenylkaempferol.

From the stem bark, three isoflavones (5,4′-dihydroxy-8-(3,3-dimethylallyl)-2″-methoxyisopropylfurano[4,5:6,7]isoflavone (1), 5,7,4′-trihydroxy-6-(3,3-dimethylallyloxiranylmethyl)isoflavone (2) and 5,4′-dihydroxy-8-(3,3-dimethylallyl)-2″-hydroxymethyl-2″-methylpyrano[5,6:6,7]isoflavone (3)) and a new isoflavanone, 5,4′-dihydroxy-2′-methoxy-8-(3,3-dimethylallyl)-2″,2″-dimethylpyrano[5,6:6,7]isoflavanone (4), together with seven known compounds, euchrenone b10 (5), isoerysenegalensein E (6), wighteone (7), laburnetin (8), lupiwighteone (9), erythrodiol (10) and oleanolic acid (11), were isolated ( Li et al. 2006). Genistein derivatives mainly in the form of prenylgenistein from this extract, including 6-prenylgenistein, 8-prenylgenistein and 6, 8-diprenylgenistein, were isolated from the stem bark (Zhang et al. 2008). Warangalone 8(3,3-dimethyl-allyl)-4′-hydroxy-2‴,2‴-imethylpyran[6,7,b]isoflavon was isolated from the stem bark (Herlina et al. 2009). The following secondary metabolites were isolated from the stem bark: alpinum isoflavone, 6-hydroxygenistein, 3β,28-dihydroxyolean-12-ene, epilupeol (Rahman et al. 2007) and three isoflavones (scandenone, 4′,5,7-trihydroxy-8-prenylisoflavone and 4′,5,7-trihydroxy-8-methylisoflavone) (Rahman et al. 2010). Liu et al. (2012) isolated erysopine and erysovine from the stem bark.

The following compounds were isolated from the roots: warangalone (scandenone), 5,7,4′-trihydroxy-6,8-diprenylisoflavone, erycristagallin, erythrabys-sin-II, phaseollin, phaseollidin, isobavachin and a cinnamylphenol, eryvariestyrene (E-1-[2, 4-dihydroxy-5-(3-methylbut-2-enyl)]-2-phenylethylene) (Telikepalli et al. 1990); pterocarpans, dihydrofolinin and erythrabyssin II, and the alkyl ester of ferulic acid, octacosyl ferulate (Ahmad et al. 2002); orientanol B (9-hydroxy3-methoxy-2γ,γ, dimethylallylpterocarpan), erycristagallin (3,9-dihydroxy-2,10-di(γ,γ-dimethylallyl)-6α,11α-dehydropterocarpan), cristacarpin, sigmoidin K, 2-(γ,γ-dimethylallyl)- 6α-hydroxyphaseollidin, erystagallin A (3,6α-dihydroxy-9-methoxy-2,10-di(γ,γ-dimethylallyl)pterocarpan) (Sato et al. 2002); two diphenylpropan-1,2-diols, eryvarinols A (1) and B (2) and their structures were elucidated as 1-(4-hydroxy-2-methoxyphenyl)-2-(4-hydroxy-3,5-dimethoxybenzoyloxy)-3-(4-hydroxyphenyl)propan-1-ol (1) and its 3″-prenyl derivative (2) (Tanaka et al. 2002a); 3,9-dihydroxy-2,10-di(γ,γ-dimethylallyl)-6α,11α-dehydropterocarpan (erycristagallin) and 9-hydroxy-3-methoxy-2-γ,γ-dimethylallylpterocarpan (orientanol B) (Tanaka et al. 2002b); two 3-phenoxychromones, eryvarins F and G, and their structures were elucidated as 3-(2,4-dihydroxyphenoxy)-7-hydroxy-6,8-di(3,3-dimethylallyl)chromen-4-one and 3-(2,4-dihydroxyphenoxy)-8-(3,3-dimethylallyl)-2,2-dimethylpyrano[5,6:6,7] chromen-4-one, respectively (Tanaka et al. 2003); three isoflavonoids, eryvarins M–O, two 2-arylbenzofurans, eryvarins P and Q, and a 3-aryl-2,3-dihydrobenzofuran, eryvarin R (Tanaka et al. 2004); two isoflavonoids, eryvarins S and T, and a new 2-arylbenzofuran, eryvarin U (Tanaka et al. 2005); a biisoflavonoid, biseryvarin A, was isolated from the roots (Tanaka et al. 2010); and two isoflavonoids, eryvarins V and W, and a chromen-4-one derivative, eryvarin X (Tanaka et al. 2011).

A 3-phenylcoumarin, indicanine A, was isolated from the root bark together with, robustic acid, daidzein and 8-prenyldaidzein (Nkengfack et al. 2000). The structure of the new compound was characterized as 4-hydroxy-5-methoxy-3-(4′-methoxyphenyl)-2″-(1-methylethenyl)dihydrofurano[4″,5″:6,7]coumarin. In addition to two known compounds, 5,4′-di-O-methylalpinumisoflavone and cajanin, a new 3-phenylcoumarin metabolite, named indicanine B, and a new isoflavone derivative, named indicanine C, were isolated from the root bark (Waffo et al. 2000). The structures of the new compounds were characterized as 4-hydroxy-3-(4′-hydroxyphenyl)-5-methoxy-2″,2″-dimethylpyrano [5″,6″:6,7] coumarin and 4′-hydroxy-5-methoxy-2″,2″-dimethylpyrano [5″,6″:6,7] isoflavone, respectively.

The crude methanol stem bark extract, n-hexane, carbon tetrachloride and chloroform soluble fractions showed moderate DPPH antioxidant activity (IC₅₀ = 484.4–82.35 μg/ml), while the purified compounds, 4′,5,7-trihydroxy-8-prenyl isoflavone alpinum isoflavone and 6-hydroxygenistein, exhibited high antioxidant activity, having IC₅₀ of 6.42, 8.30 and 8.78 μg/ml, respectively (Rahman et al. 2010). At the same time the standard compound, tert-butyl-1-hydroxytoluene (BUT), demonstrated an IC₅₀ of 5.88 μg/ml.

Studies showed that the aqueous and methanol leaf extracts exhibited significant DPPH radical scavenging activity with an IC₅₀ value of 342.59 and 283.24 μg/ml, respectively (Sakat and Juvekar 2010). The aqueous and methanol extracts significantly scavenged nitric oxide radicals (IC₅₀ = 250.12; 328.29 μg/ml, respectively). Lipid peroxidation induced by thiobarbituric acid reactive substances (TBARS) was inhibited by the aqueous extract with low IC₅₀ value (97.29 μg/ml) as compared to methanol extract (IC₅₀ = 283.74 μg/ml). Both the extracts exhibited similar quantities of total phenolics. Total flavonoids were found to be in higher quantities than total flavonols in aqueous extract as compared to methanol extract.

Among the isoflavonoids isolated from E. variegata, 3,9-dihydroxy-2,10-di(γ,γ-dimethylallyl)-6α,11α-dehydropterocarpan (erycristagallin) showed the highest antibacterial activity against mutants Streptococci, other oral Streptococci, Actinomyces and Lactobacillus species with a minimum inhibitory concentration (MIC) range of 1.56–6.25 μg/ml, followed by 3,6a-dihydroxy-9-methoxy-2,10-di(γ,γ-dimethylallyl)pterocarpan (erystagallin A) and 9-hydroxy-3-methoxy-2-γ,γ-dimethylallylpterocarpan (orientanol B) (MIC range: 3.13–12.5 μg/ml) (Sato et al. 2002).

Fourteen out of 16 isoflavonoids isolated from the roots showed antibacterial activity in the concentration range (1.56–100 μg/ml); the MIC values varied significantly among them (Tanaka et al. 2002b). Of the active compounds, 3,9-dihydroxy-2,10-di(γ,γ-dimethylallyl)-6α,11α-dehydropterocarpan (erycristagallin) and 9-hydroxy-3-methoxy-2-γ,γ-dimethylallylpterocarpan (orientanol B) exhibited the highest activity against methicillin-resistant Staphylococcus aureus with MIC values of 3.13–6.25 μg/ml. The phytochemical 2′,4′-dihydroxy-8-γ,γ-dimethylallyl-2″,2″-dimethylpyrano[5″,6″:6,7]isoflavanone (bidwillon B), isolated from Erythrina variegata, inhibited the growth of 12 methicillin-resistant Staphylococcus aureus (MRSA) strains at minimum inhibitory concentrations (MICs) of 3.13–6.25 mg/l, while MICs of mupirocin, an antibiotic, were 0.20–3.13 mg/l (Sato et al. 2004). The minimum bactericidal concentration (MBC) for bidwillon B and mupirocin against MRSA weas 6.25–25 mg/l (MBC₉₀: 12.5 mg/l) and 3.13–25 mg/l (MBC₉₀: 25 mg/l), respectively. When bidwillon B and mupirocin were combined, synergistic effects were observed for 11 strains of MRSA (fractional inhibitory concentration indices, 0.5–0.75). The MBCs of mupirocin in the presence of bidwillon B (3.13 mg/l) were reduced to 0.05–1.56 mg/l. The results suggested t bidwillon B and mupirocin to be potent phytotherapeutics, and/or their combination may be useful in the elimination of nasal and skin carriage of MRSA.

Eryvarin Q, a 2-arylbenzofuran, isolated from the roots, showed potent antibacterial activity against methicillin-resistant Staphylococcus aureus (Tanaka et al. 2004). The isoflavonoid eryvarin U, isolated from the roots, exhibited potent antibacterial activity against methicillin-resistant Staphylococcus aureus (MRSA) strains (Tanaka et al. 2005).

The crude methanol bark extract showed comparatively strong growth inhibition of Bacillus subtilis, Escherichia coli and Aspergillus niger, while n-hexane soluble fraction of the methanol extract showed poor activity against most of the test microorganisms (Rahman et al. 2007). The carbon tetrachloride fraction of the methanol extract showed moderate growth inhibition of Bacillus cereus, B. subtilis, E. coli, Pseudomonas aeruginosa, Shigella dysenteriae and Vibrio mimicus. The chloroform soluble fraction showed strong activity against B. cereus, B. subtilis, E. coli, P. aeruginosa and A. niger. The aqueous soluble fraction showed significant activity against Gram-positive bacteria, namely, B. cereus, B. subtilis, Sarcina lutea and the Gram-negative bacteria, P. aeruginosa. This fraction also showed strong activity against A. niger and Saccharomyces cerevisiae and moderate activity against Candida albicans.