In vitro antidiabetic and inhibitory potential of turmeric (Curcuma longa L) rhizome against cellular and LDL oxidation and angiotensin converting enzyme.

Turmeric (Curcuma longa L) rhizome extracts were evaluated for their antidiabetic, antihypertensive and antioxidant potentials. α-Glucosidase (0.4 µg/mL) and α-amylase (0.4 µg/mL) inhibitory potential of turmeric ethyl acetate extract was significantly higher than those of the reference drug acarbose (17.1 µg/mL and 290.6 µg/mL respectively). Protein glycation inhibitory potential of ethyl acetate extract was 800 times higher than that of ascorbic acid. High potential of ethyl acetate extract to scavenge free radicals and to reduce LDL oxidation and cellular oxidative stress was also revealed. The positive correlation obtained between the free radical scavenging capacity of the extracts and their antiglycation potential further confirmed the role of antioxidants in controlling glycation reactions. Ethyl acetate extract was also found as effective in reducing hypertension by inhibiting angiotensin converting enzyme (ACE). Antidiabetic, ACE inhibitory and antioxidant capacities of the extracts were in the order of their curcumin contents.

Turmeric (Curcuma longa L.) volatile oil inhibits key enzymes linked to type 2 diabetes.

Anti-diabetic capacity of Curcuma longa volatile oil in terms of its ability to inhibit glucosidase activities was evaluated. Turmeric volatile oils inhibited glucosidase enzymes more effectively than the reference standard drug acarbose. Drying of rhizomes was found to enhance α-glucosidase (IC50 = 1.32-0.38 µg/ml) and α-amylase (IC50 = 64.7-34.3 µg/ml) inhibitory capacities of volatile oils. Ar-Turmerone, the major volatile component in the rhizome also showed potent α-glucosidase (IC50 = 0.28 µg) and α-amylase (IC50 = 24.5 µg) inhibition.

Effects of temperature and solvent on antioxidant properties of curry leaf (Murraya koenigii L.).

Total polyphenol content (TPC) and antioxidant activities of curry leaf extracts (hexane, chloroform, ethanol, ethanol-water (1:1) and water at ambient (AT, 25 °C) and boiling temperature (BT) (Soxhlet extraction), were determined by DPPH (1,1-diphenyl-2-picrylhydrazyl), ABTS (2,2'-azinobis(3-ethylbenzothiazoline-6-sulphonic acid) diammonium salt), and total reductive potential assays. TPC was in the order ethanol-water (1:1) (AT) > water (AT) > chloroform (AT) > ethanol-water (1:1) (BT) > hexane (AT) > ethanol (BT) > water (BT) > hexane (BT). Ethanol-water (AT) had the maximum TPC of 501 ± 4.6 mg/g GAE and 82% radical scavenging activity (RSA) at 10 µg/ml level (DPPH) and 100% RSA (ABTS) at 10 µg/ml and at hot conditions (ethanol-water (BT)) had less TPC (28.7 ± 0.9%), and 43% RSA by DPPH and 53.6% by ABTS assays. Hot extracts had lesser antioxidant activities than ambient extracts. The best solvent system for getting maximum antioxidant activity from curry leaves was ethanol-water (1:1)-(AT).

Influence of cultivar and maturity at harvest on the essential oil composition, oleoresin and [6]-gingerol contents in fresh ginger from northeast India.

Severe flooding of the Brahmaputra River during the monsoon season and continuous rainfall in the northeast region (NER) of India cause an enormous loss of ginger crop every year. In this context, the present study investigates the variation in the essential oil composition and oleoresin and [6]-gingerol contents in 10 different fresh ginger cultivars harvested at 6- and 9-month maturity from five different states of NER. Monoterpenes, sesquiterpenes, and citral composition in the essential oil were evaluated to ascertain their dependence upon the maturity of ginger. Except Mizoram Thinglaidum, Mizoram Thingria, Nagaland Nadia, and Tripura I ginger cultivars, all other cultivars showed an increase in the citral content during the maturity that was observed for the first time. At 6-month maturity, a higher undecanone level was found in Nagaland Nadia (7.36 ± 0.61%), Tripura I (6.23 ± 0.61%), and Tripura III (9.17 ± 0.76%) cultivars, and these data can be used as a benchmark to identify those immature varieties. Interestingly, the Nagaland Nadia cultivar showed higher ar-curcumene (9.57 ± 0.58%) content than zingiberene (5.84 ± 0.24%), which was unique among all cultivars. Ginger harvested at 9-month maturity from the Tripura II cultivar had the highest citral content (22.03 ± 0.49%), and the Meghalaya Mahima cultivar had the highest zingiberene content (29.89 ± 2.92%). The oleoresin content was found to decrease with maturity in all cultivars, except Assam Fibreless and Manipur I. Moreover, the highest oleoresin (11.43 ± 0.58 and 9.42 ± 0.63%) and [6]-gingerol (1.67 ± 0.03 and 1.67 ± 0.05 g) contents were observed for Tripura II and Nagaland Nadia, respectively. This study suggests that Tripura and Nagaland are the most ideal locations in NER for ginger cultivation to obtain high yields of oleoresin and [6]-gingerol contents and harvesting at the 6-month maturation will compensate for the loss of ginger crop caused by the Brahmaputra River flooding in NER every year.

Essential oil composition of two unique ginger (Zingiber officinale Roscoe) cultivars from Sikkim.

Volatile oils from two most popular cultivars from Sikkim namely, Bhaisa and Majulay, were isolated, characterised by analytical GC and GC-MS. Sixty constituents accounting for 94.9% and 92.6% of the Bhaisa and Majulay oils were identified. The major compounds of Bhaisa oil were geranyl acetate (18.8%), zingiberene (16.3%) and geranial (8.2%) and those of Majulay oil were zingiberene (19.8%) and geranial (16.5%). Compared to other ginger cultivar oils, the Bhaisa oil had higher content of oxygenated compounds (43.1%). This is the first report on the essential oils from Sikkim ginger cultivars.

Turmerin, the antioxidant protein from turmeric (Curcuma longa) exhibits antihyperglycaemic effects.

A wide range of proteinaceous inhibitors are present in plants to protect themselves from hydrolytic enzymes. In this study, turmerin, a water-soluble peptide in turmeric rhizomes, was evaluated for its inhibitory potential against glucosidase and its antioxidant (AO) capacity. Turmerin inhibited α-amylase and α-glucosidase activities with IC50 values 31 and 192 µg mL⁻¹, respectively. Under the experimental conditions, those values for a standard glucosidase inhibitor, acarbose, were 81 and 296 µg mL⁻¹, respectively. The AO capacity of turmerin was evaluated using in vitro assay systems. Turmerin showed good DPPH (IC50 = 29 µg mL⁻¹) and superoxide (IC50 = 48 µg mL⁻¹) and moderate ABTS (IC50 = 83 µg mL⁻¹) radical scavenging and Fe(II) chelation (IC50 = 101 µg mL⁻¹) capacities. The inhibitory potential showed by turmerin against enzymes linked to type 2 diabetes, as well as its moderate AO capacity, could rationalise the traditional usage of turmeric rhizome preparations against diabetes.