Five compounds were isolated from the leaves (Varshney et al. 1973). Compounds A, B and C were found to be saturated higher aliphatic fatty alcohols and formed 2:4-dinitrophenylhydrazone derivatives, compound D gave all characteristics of a sterol, and compound E was identified as an anthraquinone pigment, emodin (1,6,8-trihydroxy-3-methylanthraquinone). Di-(2-ethyl) hexyl phthalate was isolated from Cassia auriculata leaves (Nageswara Rao et al. 2000). Leaves were reported to contain carbohydrates, phenols, lipids, proteins, saponins, flavonoids, tannin, terpenoids and cardiac glycosides (Senthilkumar and Vijayakumari 2012). Thirteen bioactive compounds were identified in the ethanol leaf extract, and the major constituents were phytol, octadecane 1-(ethenyloxy)- and E-10-pentadecenol. Other components included resorcinol; 3-O-methyl-d-glucose; 1,14-tetradecanediol; 3,7,11,15-tetramethyl-2-hexadecen-1-ol; 2H-cyclopropa[a]naphthalen-2-one,1,1a,4,5,6,7,7a,7b-octahydro-,1,7,7-tetramethyl-(1aa,7a,7aa,7ba)-; azulene, 1,2,3,5,6,7,8,8a-octahydro-1,4-dimethyl-7-(1-methylethenyl)-, [1S-(1a,7a,8aa)]-; 1,2-benzenedicarboxylic acid, diisooctyl ester; squalene; 1-cyclohexylnonene; and 1-4-[(2-diethylamino]ethylamino[-6-methyl-2-pyrimidinyl]-3-[3,4,5-trimethoxyphenyl] guanidine.

Twenty-nine compounds were found in C. auriculata leaves (Anandan et al. 2011). The main constituents were 3-O-methyl-d-glucose (48.50 %), α-tocopherol-β-d-mannoside (14.22 %), resorcinol (11.80 %), n-hexadecanoic acid (3.21 %), 13-octadecenal, (Z)- (2.18 %), 1,2,3,4-tetrahydroisoquinolin-6-ol-1-carboxylic acid (1.98 %), unknown (3.29 %), unknown (2.61 %) and unknown (1.14 %). Other minor constituents were glycerine (0.16 %), thymine (0.11 %), 1-butanol, 3methyl-, formate (0.17 %), 4H-pyran-4-one,2,3-dihydro-3,5-dihydroxy-6-methyl (0.46 %), benzaldehyde,4 methyl- (0.83 %), 2-propenoic acid, 4-methylpentyl ester (0.125), sucrose (1.2 %), 1,6,anhydro-β-d-glucopyranose (levoglucosan) (0.3 %), β-d-glucopyranoside, methyl (0.36 %), 1,2-benzenedicarboxylic acid, bis(2-methylpropyl)ester (1 %), benzenamine,2,3,4,5,6-pentamethyl (0.87), unknown (0.57 %), hexadecanoic acid, ethyl ester (0.1 %), 1-tridecyne (0.3 %), 13-oxabicyclo[10.1.0] tridecane (0.42 %), phytol (0.61 %), 1-E,11,Z-13-octadecatriene (0.56 %), 1 octadecanoic acid (0.46 %), a-tocopherol (1.16 %) and N-acetyl tyramine (1.24 %).

Sterols, anthracene derivatives, triterpenoid and tannins were isolated from the ethanol extract of the pods (Suresh et al. 2007).

The following chemicals were identified in the seed extract: n-hexadecanoic acid (21.31 %), grapeseed oil (linoleic and oleic acids) (31.02 %), E,Z-1,3,12-nonadecatriene (12.27 %), stearic acid (9.39 %), benzoic acid, 2-hydroxy-methyl ester (0.07 %), β-ethoxypropionaldehyde diethyl acetal (0.86 %), ethyl caprylate (0.14 %), 2-methoxy-4-vinylphenol (0.36 %), glycine, N-(trifluoroacetyl)-, 1-methylbutyl ester (0.10 %), 2,3-dihydro-3,5-dihydroxy-6-methyl-4H-pyran-4-one (0.12 %), capric acid ethyl ester (0.16 %), resorcinol (0.21 %) dodecanoic acid (0.48 %), 3′5′-dimethoxyacetophenone (0.58 %), 9-octadecenoic acid, (E)-(12.60 %), palmitic acid β-monoglyceride (2.95 %), dl-α-tocopherol (1.22 %) and stigmasta-5,23-dien-3-ol,(3β)- (1.21 %) (Raj et al. 2012).

Polyphenols quantified in the hydroalcoholic seed extract of C. auriculata were epicatechin (14 %), catechin (4.5 %) and procyanidin B1 (1 %), while the supercritical fluid extract contained catechin (6 %) and epicatechin gallate (20 %) (Puranik et al. 2011).

The flower of C. auriculata was found to contain a flavonol glycoside 5-O-methylquercetin 7-O-glucoside (Manogaran and Sulochana 2004). The hydromethanolic extract and its ethyl acetate and n-butanol fractions of the flowers were found to contain phenolic compounds, carbohydrates, tannins, steroids and amino acids (Surana et al. 2009).

Phytochemical analysis of the crude root extracts revealed the presence of an array of active chemical constituents such as tannins, flavonoids, glycosides, carbohydrates, steroids and triterpenoids (Wadekar et al. 2011).

C. auriculata was reported to contain leucopelargonidins, flavan-3,4-diols of the ‘phloroglucinol series’ (Paris and Cubukcu 1962). From the aerial plant parts, the following compounds were isolated: kaempferol-3-O-rutinoside, rutin, kaempferol, quercetin and luteolin (Juan-Badaturuge et al. 2011; Habtemariam 2013), and oleanolic acid (Senthilkumar and Reetha 2011).

Some of the reported pharmacological properties of the various plant parts of Cassia auriculata are elaborated below.

The ethanol and methanol extracts of C. auriculata flowers showed antioxidant activity in both 2,2′-azinobis-(3-ethylbenzothiazoline-6-sulfonic acid) (ABTS) and 1,1-diphenyl-2-picrylhydrazyl (DPPH) radical scavenging assays (Kumaran and Karunakaran 2007). The flower powder of Cassia auriculata significantly decreased the thiobarbituric acid reactive substances (TBARS), hydroperoxide and conjugated dienes and increased the antioxidant enzymes (catalase, superoxide dismutase and glutathione peroxidase) and nonenzymatic antioxidants (ascorbic acid, vitamin E and reduced glutathione) in streptozotocin-induced diabetic rats (Jeyashanthi and Ashok 2010). The antioxidative effect of 200 mg/kg body weight (bw) of the extract was significantly better than 100 mg/kg body weight extract and the reference drugs (tolbutamide and metformin). Antioxidative effect was not observed in normoglycemic rats in the experiment. In another study, oral administration of C. auriculata aqueous leaf extract to streptozotocin-induced mild diabetic (MD) and severe diabetic (SD) rats (100, 200 and 400 mg/kg bw per day for a period of 21 days) produced significant fall in fasting blood glucose (FBG) in a dose-dependent manner (Gupta et al. 2009c). Treatment with the extract (400 mg/kg) showed significant reduction in serum levels of thiobarbituric acid reactive substances (TBARS) and oxidized low-density lipoprotein (OxLDL) in both MD and SD rats. The antioxidant defence system was also found to be improved in extract-treated (400 mg/kg) MD and SD rats, as revealed by significant increase in activities of erythrocyte’s antioxidant enzymes, that is, superoxide dismutase (SOD) and catalase (CAT) with a concomitant elevation in erythrocyte’s reduced glutathione (GSH) content. Moreover, there were no toxic signs in rats treated with high doses of the extract (1,000 and 2,000 mg/kg bw per day for 21 days). Blood glucose, hepatic and renal function parameters in these rats were found within normal limits.

The alcoholic extract of the aerial part of C. auriculata exhibited potent antioxidant activity when assessed by DPPH radical scavenging, lipid peroxidation and reducing power analysis (Juan-Badaturuge et al. 2011). Fractionation of the crude extract showed that the ethyl acetate fraction was the most active followed by the chloroform fraction, while the petroleum ether, n-butanol and water fractions were less active than the crude extract.

Cassia auriculata leaf ethanol extract dose-dependently inhibited the growth of human breast adenocarcinoma MCF-7 and human larynx carcinoma Hep-2 cell lines in vitro with IC50 values of 400 and 500 μg through induction of apoptosis (Prasanna et al. 2009). The MCF-7 and Hep-2 cells showed decreased expression of antiapoptotic Bcl-2 protein and increased expression of Bax/Bcl-2 ratio upon treatment. When Cassia auriculata extract and curcumin were combined, a synergistic effect of anticancer activity at a much lower concentration of both was noted (Prasanna et al. 2011).

Cassia auriculata leaf extract exhibited significant broad spectrum activity in-vitro against Bacillus subtilis and S. aureus (Samy and Ignacimuthu 2000). Studies conducted in birds with Escherichia coli infection showed that C. auriculata herbal extract had more potent microbicidal activity compared to Piper betle (Prakash 2006). The methanol leaf extract (5 mg/disc) and methanol flower extract (2.5 mg/disc) showed in-vitro growth inhibitory activity against Bacillus subtilis, Staphylococcus aureus, Staphylococcus epidermidis and Enterococcus faecalis (Duraipandiyan et al. 2006). The methanol flower extract (5 mg/disc) showed antibacterial activity against all four bacteria and Escherichia coli.

The ethanol, methanol and aqueous extracts of dry flowers and ethanol, methanol and acetone extracts of fresh flowers of Cassia auriculata exhibited in-vitro antibacterial activity against Staphylococcus aureus, Enterococcus faecalis, Bacillus subtilis, Salmonella typhi, Salmonella paratyphi A, Escherichia coli, Proteus mirabilis, Pseudomonas aeruginosa, Klebsiella pneumoniae, Vibrio cholerae and Shigella dysenteriae (Maneemegalai and Naveen 2010). The maximum activity was observed against all organisms except Pseudomonas aeruginosa and Klebsiella pneumoniae. The minimum inhibitory concentration ranged between 12.5 and 75 mg/mL depending on microorganism and various extract. Presence of phytochemicals such as terpenoids, tannins, flavonoids, saponin, cardiac glycosides and steroids was observed. Of several plant species, Cassia auriculata was selected as the efficient plant, which showed antibacterial activity against Escherichia coli, Salmonella typhi, Proteus mirabilis and Klebsiella pneumoniae at different concentrations Senthilkumar and Reetha 2011).

The 50 % acetone flower extract of C. auriculata showed marked antiinflammatory activity (56 %) in carrageenan-induced oedema in rats (Manogaran and Sulochana 2004).

Administration of aqueous Cassia auriculata flower extract at 0.45 g/kg significantly decreased blood glucose, glycosylated haemoglobin and gluconeogenic enzymes and increased plasma insulin, haemoglobin and hexokinase activity in streptozotocin diabetic rats (Latha and Pari 2003a). The elevated gluconeogenesis during diabetes was reverted to normal by the extract in enhancing the utilization of glucose through increased glycolysis. The effect of the extract was more prominent than that of glibenclamide. The methanol flower extract of C. auriculata was found to have potential alpha-glucosidase inhibitory activity in vitro, preferably on maltase with a low IC₅₀ value of 0.023 mg/mL and inhibited the maltase activity competitively (Abesundara et al. 2004). Oral administration of C. auriculata methanol extract in Sprague–Dawley rats significantly and potently lowered blood glycemic response towards maltose ingestion which was observed at 30 minutes after dosing of 5 mg/kg, thus concurrently suppressed insulin activity. The ED₅₀ of the extract (4.9 mg/kg) clearly indicated that the antihyperglycemic effect was as potent as that of therapeutic drug, acarbose (ED₅₀ 3.1 mg/kg). In another study, oral administration of water-soluble fraction of the ethanol extract of C. auriculata flowers to alloxan diabetic rats significantly reduced blood glucose level and elevated plasma insulin level compared to the aqueous extract-treated rats and diabetic control (Hakkim et al. 2007). Treatment with water-soluble fraction of ethanol extract and aqueous extract of C. auriculata flowers restored altered hyperlipidaemic parameters and enzymatic markers in diabetic animals. The water-soluble fraction of the ethanol extract exerted a more efficient antihyperglycemic effect compared to the aqueous extract. Surana et al. (2009) reported that the n-butanol fraction of the hydromethanol flower extract exhibited significant reduction in blood glucose levels and was also found effective in restoring the blood lipids and proteins to normal level. The activity was found comparable with standard drug phenformin. The flower and leaf extracts of Cassia auriculata exerted a significant reduction in the serum glucose and triglycerides and cholesterol levels and increase in the plasma insulin levels in alloxan-induced diabetic rats when compared to root and stem extracts (Umadevi et al. 2006).