Short Overview of Some Assays for the Measurement of Antioxidant Activity of Natural Products and Their Relevance in Dermatology

Impaired systemic redox homeostasis is implicated in the onset and development of various diseases, including skin diseases. Therefore, continuous search for natural products with antioxidant bioactivities applicable in biomedicine is attractive topic of general interest. Research efforts aiming to validate antioxidant potentials of natural products has led to the development of several assays based on various test principles. Hence, understanding the advantages and limitations of various assays is important for selection of assays useful to study antioxidant and related bioactivities of natural products of biomedical interest. This review paper gives a short overview on some chemical and cellular bioassays used to estimate the antioxidant activity of chosen natural products together with a brief overview on the use of natural products with antioxidant activities as adjuvant medicinal remedies in dermatology.

In vitro antidiabetic, antioxidant activities and GC-MS analysis of Rhynchostylis Retusa and Euphorbia Neriifolia leaf extracts

This study aimed to assess the antidiabetic, and antioxidant potential of Rhynchostylis retusa and Euphorbia neriifolia, well known for traditional ethnomedicinal uses in North-east India. Leaf extracts prepared in water, methanol and petroleum ether were evaluated for in vitro antidiabetic and antioxidant assay using α-amylase inhibition, glucose diffusion method and DPPH radical scavenging activity. The α-amylase inhibition with E. neriifolia methanolic extract at 400 μg/ml (66.67%) and R. retusa aqueous extract at 300 μg/ml (58.15%) were stronger than in equivalent concentrations of acarbose, i.e., 62.17, and 51.52%, respectively. Aqueous extract R. retusa showed a maximum 67.65% inhibition of glucose diffusion at 180 min in comparison to control without leaf extract. The DPPH radical scavenging activity of E. neriifolia extract in methanol was significantly better than equivalent aqueous or ether extract. However, the solvent choice had little impact on antioxidant activity in R. retusa. GC-MS analysis revealed the presence of a large number of phytochemicals in methanol fraction of E. neriifolia aqueous extracts in comparison to R. retusa. Though the in vitro α-amylase inhibition or glucose diffusion retardation implied potential medicinal use of endangered orchid R. retusa and E. neriifolia, further investigation may be warranted for identification of relevant bio-active compounds and in vivo validation of their pharmacological properties.

Chemical Constituent of β-Glucuronidase Inhibitors from the Root of Neolitsea acuminatissima

Neolitsea acuminatissima (Lauraceae) is an endemic plant in Taiwan. One new carboline alkaloid, demethoxydaibucarboline A (1), two new eudesmanolide-type sesquiterpenes, methyl-neolitacumone A (2), neolitacumone E (3), and twelve known compounds (4-15) were isolated from the root of Neolitsea acuminatissima. Their structures were elucidated by spectroscopic analysis. Glucuronidation represents a major metabolism process of detoxification for carcinogens in the liver. However, intestinal bacterial β-Glucuronidase (βG) has been considered pivotal to colorectal carcinogenesis. To develop specific bacterial-βG inhibitors with no effect on human βG, methanolic extract of roots of N. acuminatissima was selected to evaluate their anti-βG activity. Among the isolates, demethoxydaibucarboline A (1) and quercetin (8) showed a strong bacterial βG inhibitory effect with an inhibition ratio of about 80%. Methylneolitacumone A (2) and epicatechin (10) exhibited a moderate or weak inhibitory effect and the enzyme activity was less than 45% and 74%, respectively. These four compounds specifically inhibit bacterial βG but not human βG. Thus, they are expected to be used for the purpose of reducing chemotherapy-induced diarrhea (CID). The results suggest that the constituents of N. acuminatissima have the potential to be used as CID relief candidates. However, further investigation is required to determine their mechanisms of action.

Chemical Composition, Antibacterial and α-Glucosidase Inhibitory Activities of the Essential Oils of Neolitsea coccinea (Lauraceae)

The chemical composition, antibacterial and α-glucosidase inhibitory activities of the essential oils obtained from hydrodistillation of the fresh stem and leaf of Neolitsea coccinea B. C. Stone are reported for the first time. GC and GC-MS analysis revealed the presence of 42 volatile compounds from the stem and leaf oils, accounting for 84.9% and 90.4%, respectively of the identified components. The principle compounds in the stem oil were δ-cadinene (21.2%), 1-epi-cubenol (11.3%) and cyperotundone (10.7%), while the main compounds in the leaf oil were selin-11-en-4-α-ol (26.8%), bicyclogermacrene (12.6%), γ-eudesmol (7.1%), germacrene D (6.1%) and globulol (5.9%). The leaf oil demonstrated moderate to weak antibacterial activity towards Bacillus subtilis and Staphylococcus aureus with MIC values of 250 μg/mL and 500 μg/mL, respectively, whereas the stem oil possessed weak antibacterial activity against B. subtilis with a MIC value of 500 μg/mL. The stem and leaf oils showed significant α-glucosidase inhibitory activity with IC50 values of 32.2 ± 0.8 μg/mL and 70.9 ± 1.1 μg/mL, respectively.

Characterization and metal-induced gene transcription of two new copper zinc superoxide dismutases in the solitary ascidian Ciona intestinalis

Antioxidant enzymes are known to protect living organisms against the oxidative stress risk, also induced by metals. In the present study, we describe the purification and molecular characterization of two Cu,Zn superoxide dismutases (SODs), referred to as Ci-SODa and Ci-SODb, from Ciona intestinalis, a basal chordate widely distributed in temperate shallow seawater. The putative amino acid sequences were compared with Cu,Zn SODs from other metazoans and phylogenetic analyses indicate that the two putative Ci-SODs are more related to invertebrate SODs than vertebrate ones. Both phylogenetic and preliminary homology modeling analyses suggest that Ci-SODa and Ci-SODb are extracellular and intracellular isoform, respectively. The mRNA of the two Cu,Zn SODs was localized in hemocytes and in ovarian follicular cells, as revealed by in situ hybridization. The time course of SOD mRNA levels in the presence of three different metals showed upregulation of ci-soda and inhibition of ci-sodb. Spectrophotometric analysis confirms the presence of SOD activity in Ciona tissues. Our in silico analyses of the ci-soda promoter region revealed putative consensus sequences similar to mammalian metal-responsive elements (MRE), suggesting that the transcription of these genes directly depends on metals. These data emphasize the importance of complex metal regulation of ci-soda and ci-sodb transcription, as components of an efficient detoxification pathway allowing the survival of C. intestinalis in continued, elevated presence of metals in the environment.

Composition and in vitro Anticancer Activities of the Leaf Essential Oil of Neolitsea variabillima from Taiwan

This study investigated the chemical composition and in vitro anticancer activities of the essential oil isolated from the leaf of Neolitsea variabillima. The essential oil was isolated using hydrodistillation in a Clevenger-type apparatus, and characterized by GC-FID and GC-MS. Sixty-seven compounds were identified, representing 100% of the oil. The main components identified were trans-β-ocimene (13.4%), α-cadinol (10.5%), terpinen-4-ol (9.3%), τ-cadinol (9.2%), β-caryophyllene (8.8%), and sabinene (6.7%). The anticancer activities of oil were evaluated. The results showed that the oil exhibited cytotoxic activity against human oral, liver, lung, colon, melanoma, and leukemic cancer cells. The presence of β-caryophyllene, τ-cadinol, and α-cadinol significantly contributed to the anticancer activities of N. variabillima leaf oil.