Insecticidal and Nematicidal Activities of Novel Mimosine Derivatives.

Mimosine, a non-protein amino acid, is found in several tropical and subtropical plants, which has high value for medicine and agricultural chemicals. Here, in continuation of works aimed to development of natural product-based pesticidal agents, we present the first significant findings for insecticidal and nematicidal activities of novel mimosine derivatives. Interestingly, mimosinol and deuterated mimosinol (D-mimosinol) from mimosine had strong insecticidal activity which could be a result of tyrosinase inhibition (IC50 = 31.4 and 46.1 µM, respectively). Of synthesized phosphoramidothionate derivatives from two these amino alcohols, two compounds (1a and 1b) showed high insecticidal activity (LD50 = 0.5 and 0.7 µg/insect, respectively) with 50%-60% mortality at 50 µg/mL which may be attributed to acetylcholinesterase inhibition. Compounds 1a and 1b also had strong nematicidal activity with IC50 = 31.8 and 50.2 µM, respectively. Our results suggest that the length of the alkyl chain and the functional group at the C5-position of phosphoramidothionates derived from mimosinol and d-mimosinol are essential for the insecticidal and nematicidal activities. These results reveal an unexplored scaffold as new insecticide and nematicide.

Hispidin and related herbal compounds from Alpinia zerumbet inhibit both PAK1-dependent melanogenesis in melanocytes and reactive oxygen species (ROS) production in adipocytes.

Recently several compounds from Okinawa plants including Alpinia zerumbet (alpinia) were shown to inhibit directly the oncogenic/ageing kinase PAK1 (p21-activated kinase 1). Furthermore, it was recently revealed that both PAK1 and PAK4 (p21-activated kinase 4) are equally essential for the melanogenesis in melanoma cells. Thus, in this study, we tested if several alpinia compounds inhibit the melanogenesis in melanoma (B16F10) cells, as well as the PAK1-dependent up-regulation of both reactive oxygen species (ROS) and nitric oxide (NO) in cultured adipocytes (3T3-L1) without any cytotoxicity. The effect of alpinia compounds on the melanogenesis was measured by both the melanin content and intracellular tyrosinase activity in melanoma cells treated with 3-isobutyl-1-methylxanthine (IBMX), a melanogenesis stimulating hormone. We found that (1E,3E,5E)-6-methoxyhexa-1,3,5-trien-1-yl)-2,5-dihydrofuran (MTD), 5,6-dehydrokawain (DK), labdadiene, hispidin and dihydro-5,6-dehydrokawain (DDK) at 50 µg/mL reduced the melanin content by 63-79%. The MTD, DK and hispidin, at 50 µg/mL, inhibited tyrosinase activity by 70-83% in melanoma cells. Among these compounds, labdadiene, MTD, (E)-2,2,3,3-Tetramethyl8-methylene-7-(oct-6-en-1-yl)octahydro-1H-quinolizine (TMOQ) and hispidin strongly inhibited the ROS production. Hispidin, labdadiene and MTD at 20 µg/mL inhibited NO production by over 70%. These findings altogether suggest that some of these alpinia compounds could be potentially useful for the prevention or treatment of hyperpigmentation and obesity.

Significant longevity-extending effects of Alpinia zerumbet leaf extract on the life span of Caenorhabditis elegans.

The beneficial effects of the phytochemical compounds in fruits and vegetables have been extrapolated mainly from in vitro studies or short-term dietary supplementation studies. Recent approaches using animal models of Caenorhabditis elegans are becoming quite popular, and in this regard the effects of Alpinia zerumbet leaf extract (ALP) on C. elegans lifespan were investigated under both normal and stress conditions. ALP significantly increased, mean lifespan by 22.6%, better than the positive control, resveratrol. Furthermore, both under thermal and oxidative stressed conditions, ALP increased the survival rate significantly better than quercetin. Further studies indicated that the significant longevity-extending effects of ALP on C. elegans can be attributed to its in vitro free-radical scavenging effects and its upregulation of stress-resistance proteins, including superoxide dismutase 3 (SOD-3) and heat-shock protein (HSP-16.2). These results suggest that phytochemical compounds in A. zerumbet have beneficial effects on the lifespan of C. elegans, and that they can be used as a source of dietary supplements for aging and age-related diseases.

Effect of Alpinia zerumbet components on antioxidant and skin diseases-related enzymes.

BACKGROUND: The skin is chronically exposed to endogenous and environmental pro-oxidant agents, leading to the harmful generation of reactive oxygen species. Antioxidant is vital substances which possess the ability to protect the body from damage cause by free radicals induce oxidative stress. Alpinia zerumbet, a traditionally important economic plant in Okinawa, contains several interesting bioactive constituents and possesses health promoting properties. In this regard, we carried out to test the inhibitory effect of crude extracts and isolated compounds from A. zerumbet on antioxidant and skin diseases-related enzymes. METHODS: The antioxidant activities were examined by DPPH, ABTS and PMS-NADH radical scavenging. Collagenase, elastase, hyaluronidase and tyrosinase were designed for enzymatic activities to investigate the inhibitory properties of test samples using a continuous spectrophotometric assay. The inhibitory capacity of test samples was presented at half maximal inhibitory concentration (IC50). RESULTS: The results showed that aqueous extract of the rhizome was found to have greater inhibitory effects than the others on both of antioxidant and skin diseases-related enzymes. Furthermore, 5,6-dehydrokawain (DK), dihydro-5,6-dehydrokawain (DDK) and 8(17),12-labdadiene-15,16-dial (labdadiene), isolated from rhizome, were tested for antioxidant and enzyme inhibitions. We found that DK showed higher inhibitory activities on DPPH, ABTS and PMS-NADH scavenging (IC50 = 122.14 ± 1.40, 110.08 ± 3.34 and 127.78 ± 4.75 µg/ml, respectively). It also had stronger inhibitory activities against collagenase, elastase, hyaluronidase and tyrosinase (IC50 = 24.93 ± 0.97, 19.41 ± 0.61, 19.48 ± 0.24 and 76.67 ± 0.50 µg/ml, respectively) than DDK and labdadiene. CONCLUSION: Our results indicate that the rhizome aqueous extract proved to be the source of bioactive compounds against enzymes responsible for causing skin diseases. Moreover, DK could be used as a potent inhibitor and be further exploited to be used in anti-skin disease formulations.

Antiatherogenic properties of acetone extract of Alpinia zerumbet seeds.

Oxidation of low-density lipoprotein (LDL) is the principal risk factor for the development of atherosclerosis. In this study, we used several methods to investigate the ability of the acetone extract from rhizomes, stems, leaves, flowers, pericarps and seeds of Alpinia zerumbet to inhibit atherosclerosis in vitro. The seed extract had the strongest activity against tyrosinase, pancreatic lipase (PL), 15-lipoxygenase (15-LO) and LDL oxidation activities (IC50 = 2.30 ± 0.02, 5.00 ± 0.07, 1.29 ± 0.07 and 15.40 ± 0.86 µg/mL, respectively), amongst all different parts. It also had similar effects to the positive controls. Most of the extracts showed partial agonistic properties towards estrogenic activity. Cholest-4-ene-3,6-dione, a steroid present only in the seed extract seems to be the compound responsible for these activities. The results showed that cholest-4-ene-3,6-dione had similar ability to curcumin and quercetin against PL and LDL oxidation (IC50 = 19.50 ± 1.17 and 16.12 ± 1.43 µg/mL, respectively). Furthermore, cholest-4-ene-3,6-dione (IC50 = 34.21 ± 1.31 µg/mL) had higher inhibition against 15-LO than quercetin (IC50 = 54.79 ± 1.12 µg/mL).

Antioxidant, antimicrobial, 15-LOX, and AGEs inhibitions by pineapple stem waste.

UNLABELLED: Pineapple stem has been extensively used for bromelain extraction; however, almost no attention has been given to the waste obtained during bromelain manufacturing. In this regard, antioxidant, antimicrobial, and inhibitions against 15-lipoxygenase and advanced glycation end product formations by pineapple stem waste (PSW) obtained during bromelain manufacturing process were studied. The PSW had moderate bioactivities in all the performed assays. It also showed a considerable inhibition against fungal growth, probably due to high amounts of the benzoic acid present in the sample. These results indicate that PSW could be utilized as an economic source of preventive or therapeutic agent in disease and in different functional food industries. PRACTICAL APPLICATION: A large amount of wastes are generated during bromelain manufacturing from pineapple stem. So far, these wastes are not utilized and are often considered as a burden while disposing them. However, we found some important phytochemicals with considerable bioactivities in these wastes. We believe that these wastes may have a promising usage as a cheap source of one of the ingredients in functional food based industries.

Solid-phase synthesis of mimosine tetrapeptides and their inhibitory activities on neuraminidase and tyrosinase.

Neuraminidase is a rational target for influenza inhibition, and the search for neuraminidase inhibitors has been intensified. Mimosine, a nonprotein amino acid, was for the first time identified as a neuraminidase inhibitor with an IC(50) of 9.8 ± 0.2 µM. It was found that mimosine had slow, time-dependent competitive inhibition against the neuraminidase. Furthermore, a small library of mimosine tetrapeptides (M-A(1)-A(2)-A(3)) was synthesized by solid-phase synthesis and was assayed to evaluate their neuraminidase and tyrosinase inhibitory properties. Most of the tetrapeptides showed better activities than mimosine. Mimosine-FFY was the best compound, and it exhibited 50% neuraminidase inhibition at a low micromolar range of 1.8 ± 0.2 µM, whereas for tyrosinase inhibition, it had an IC(50) of 18.3 ± 0.5 µM. The kinetic studies showed that all of the synthesized peptides inhibited neuraminidase noncompetitively with K(i) values ranging from 1.9 -to 7.2 µM. These results suggest that mimosine could be used as a source of bioactive compounds and may have possibilities in the design of drugs as neuraminidase and tyrosinase inhibitors.

HIV-1 integrase and neuraminidase inhibitors from Alpinia zerumbet.

AIDS and influenza are viral pandemics and remain one of the leading causes of human deaths worldwide. The increasing resistance of these diseases to synthetic drugs demands the search for novel compounds from plant-based sources. In this regard, the leaves and rhizomes of Alpinia zerumbet, a traditionally important economic plant in Okinawa, were investigated for activity against HIV-1 integrase (IN) and neuraminidase (NA). The aqueous extracts of leaves and rhizomes had IN inhibitory activity with IC(50) values of 30 and 188 µg/mL, whereas against NA they showed 50% inhibition at concentrations of 43 and 57 µg/mL, respectively. 5,6-Dehydrokawain (DK), dihydro-5,6-dehydrokawain (DDK), and 8(17),12-labdadiene-15,16-dial (labdadiene) were isolated from the rhizomes and were tested for enzyme inhibitions. DK and DDK strongly inhibited IN with IC(50) of 4.4 and 3.6 µg/mL, respectively. Against NA, DK, DDK, and labdadiene exhibited mixed type of inhibition with respective IC(50) values of 25.5, 24.6, and 36.6 µM and K(i) values ranging from 0.3 to 2.8 µM. It was found that DDK is a slow and time-dependent reversible inhibitor of NA, probably with a methoxy group as its functionally active site. These results suggest that alpinia could be used as a source of bioactive compounds against IN and NA and that DK and DDK may have possibilities in the design of drugs against these viral diseases.

Advanced glycation end products inhibitors from Alpinia zerumbet rhizomes.

Advanced glycation end products (AGEs) are major factors responsible for the complication of diabetes. The present study was carried out to investigate the inhibitory activities on fructosamine adduct and α-dicarbonyl formations by hexane extracts of various parts of Alpinia zerumbet. Furthermore, we isolated two previously known compounds, namely 5,6-dehydrokawain (DK) and dihydro-5,6-dehydrokawain (DDK). 8(17),12-Labdadiene-15,16-dial (labdadiene) was isolated for the first time from the rhizome of A. zerumbet. The results showed that labdadiene (IC50=51.06µg/mL) had similar activity to rutin and quercetin against fructosamine adduct. The inhibition of α-dicarbonyl compounds formation by labdadiene was significantly higher than that of DK and DDK. Our results indicate that labdadiene is a potent antiglycation agent which was found to inhibit AGEs formation in three different steps in the pathway. These data indicate that labdadiene could be used to prevent glycation-associated complications in diabetes.