1,720,970 research outputs found
Bioactivity and chemical investigations of Pereskia Bleo and Pereskia Grandifollia / Sim Kae Shin
Full text linkEthnopharmacological data has been one of the common useful criteria in drug discovery. Pereskia bleo and Pereskia grandifolia (Cactaceae), commonly known as
‘Jarum Tujuh Bilah’ in Malay and ‘Cak Sing Cam’ in Chinese have long been used as natural remedies in Malaysia. The experimental approach in the present study was
based on bioassay-guided fractionation. The crude methanol and fractionated extracts of both Pereskia spp. were initially investigated for their biological activities such as antioxidant, antimicrobial and cytotoxic effect against five human cancer cell lines, namely nasopharyngeal epidermoid carcinoma cell line (KB), cervical carcinoma cell line (CasKi), colon carcinoma cell line (HCT 116), hormone-dependent breast carcinoma cell line (MCF7), lung carcinoma cell line (A549) and the non-cancer human fibroblast cell line (MRC-5) using in vitro cytotoxicity assay, in order to identify the bioactive extracts of both Pereskia spp.The hexane and ethyl acetate extracts of both Pereskia spp. generally showed
stronger antioxidant activities than the other extracts. Ethyl acetate extracts of both Pereskia spp. also showed some mild antimicrobial activities against the tested bacteria.In the cytotoxicity assay, both Pereskia spp. exerted no damage to MRC-5 normal cells.The ethyl acetate extracts of both Pereskia spp. in general gave higher inhibition and stimulation values against various cancerous cell lines compared to other extracts. The
cell deaths of the selected cancer cells elicited by the cytotoxic active extracts of both Pereskia spp. were found to be apoptotic in nature based on a clear indication of DNA fragmentation, which is a hallmark of apoptosis. In addition, the LUX RT-qPCR [realiii
time reverse transcriptase–polymerase chain reaction (RT-qPCR) using LUX (Light Upon eXtension) primers] analysis showed that apoptosis elicited by the cytotoxic extracts on selected cancer cells was mediated by p53, caspase-3 and c-myc activation in different expression levels.
Methyl palmitate, methyl linoleate, methyl α-linolenate and phytol were identified from the hexane extract of Pereskia bleo by GCMS analysis whilst methyl palmitate, methyl linoleate, methyl α-linolenate and methyl stearate were identified from the hexane extract of Pereskia grandifolia. From the results of the biological
screenings, it is observed that the ethyl acetate extracts generally have stronger biological activities than other extracts. Further chemical investigations were thus
directed to the ethyl acetate extracts of both Pereskia spp.2,4-Di-tert-butylphenol (1), α-tocopherol (2), phytol (3), ß-sitosterol (4),dihydroactinidiolide (5) and a mixture of sterols containing campesterol (6),
stigmasterol (7) and β-sitosterol (4) were isolated from Pereskia bleo whilst 2,4-di-tertbutylphenol
(1), α-tocopherol (2), ß-sitosterol (4) and mixture containing methyl palmitate (9), methyl oleate (10), methyl stearate (11) and 2,4-di-tert-butylphenol (1)
were isolated from Pereskia grandifolia. It is interesting to note that 2,4-ditertbutylphenol(1), α-tocopherol (2) and ß-sitosterol (4) were isolated from the ethyl
acetate extracts of both Pereskia spp. The cytotoxic activities of the isolated constituents were evaluated against the above human cell lines and further studies on
their mode of action suggested that these activities are connected with induction of apoptosis.In addition, the toxicity of both Pereskia spp. was evaluated in vivo and were considered safe in acute oral toxicities in experimental mice. The screening of the locally grown Pereskia bleo and Pereskia grandifolia indicated the presence ofalkaloids, but the concentration was very low.
The findings of Pereskia bleo and Pereskia grandifolia in the present study provided scientific validation on the use of the leaves of both Pereskia spp. for the
treatment of cancer. Further studies on the mutagenic and toxicity effect over a longer period of time involving detection of effects on vital organ functions should be carried out to ensure that the plants are safe for human consumption
Fig. 1 in Polyneurines A H, iboga alkaloids from Tabernaemontana polyneura
No full textFig. 1. Structures of compounds 1–11, 14, and 20–21.Published as part of Tang, Sin-Yee, Tan, Chun-Hoe, Sim, Kae-Shin, Yong, Kien-Thai, Lim, Kuan-Hon, Low, Yun-Yee & Lim, Siew-Huah, 2023, Polyneurines A H, iboga alkaloids from Tabernaemontana polyneura, pp. 113587 in Phytochemistry (113587) 208 on page 2, DOI: 10.1016/j.phytochem.2023.113587, http://zenodo.org/record/816067
Fig. 5 in Polyneurines A H, iboga alkaloids from Tabernaemontana polyneura
No full textFig. 5. Proposed biosynthetic pathway to 1.Published as part of Tang, Sin-Yee, Tan, Chun-Hoe, Sim, Kae-Shin, Yong, Kien-Thai, Lim, Kuan-Hon, Low, Yun-Yee & Lim, Siew-Huah, 2023, Polyneurines A H, iboga alkaloids from Tabernaemontana polyneura, pp. 113587 in Phytochemistry (113587) 208 on page 8, DOI: 10.1016/j.phytochem.2023.113587, http://zenodo.org/record/816067
Polyneurines A H, iboga alkaloids from Tabernaemontana polyneura
No full textTang, Sin-Yee, Tan, Chun-Hoe, Sim, Kae-Shin, Yong, Kien-Thai, Lim, Kuan-Hon, Low, Yun-Yee, Lim, Siew-Huah (2023): Polyneurines A H, iboga alkaloids from Tabernaemontana polyneura. Phytochemistry (113587) 208: 113587, DOI: 10.1016/j.phytochem.2023.113587, URL: http://dx.doi.org/10.1016/j.phytochem.2023.11358
Going Beyond Counting First Authors in Author Co-citation Analysis
Full text linkThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Variations on the Author
Full text link“Variations on the Author” discusses two of Eduardo Coutinho’s recent films (Um Dia na Vida, from 2010, and Últimas Conversas, posthumously released in 2015) and their contribution to the general question of documentary authorship. The director’s filmography is characterized by a consistent yet self-effacing form of authorial self-inscription: Coutinho often features as an interviewer that rather than express opinions propels discourses; an interviewer that is good at listening. This mode of self-inscription characterizes him as an author who is not expressive but who is nonetheless markedly present on the screen. In Um Dia na Vida, however, Coutinho is completely absent form the image, while Últimas Conversas, on the contrary, includes a confessional prologue that moves the director from the margins to the center of his films. This article examines the ways in which these works stand out in the filmography of a director who offers new insights into the notion of cinematic authorship
Appropriate Similarity Measures for Author Cocitation Analysis
Full text linkWe provide a number of new insights into the methodological discussion about author cocitation analysis. We first argue that the use of the Pearson correlation for measuring the similarity between authors’ cocitation profiles is not very satisfactory. We then discuss what kind of similarity measures may be used as an alternative to the Pearson correlation. We consider three similarity measures in particular. One is the well-known cosine. The other two similarity measures have not been used before in the bibliometric literature. Finally, we show by means of an example that our findings have a high practical relevance.information science;Pearson correlation;cosine;similarity measure;author cocitation analysis
Dispelling the Myths Behind First-author Citation Counts
Full text linkWe conducted a full-scale evaluative citation analysis study of scholars in the XML research field to explore just how different from each other author rankings resulting from different citation counting methods actually are, and to demonstrate the capability of emerging data and tools on the Web in supporting more realistic citation counting methods. Our results contest some common arguments for the continued
use of first-author citation counts in the evaluation of scholars, such as high correlations between author rankings by first-author citation counts and other citation
counting methods, and high costs of using more realistic citation counting methods that are not well-supported by the ISI databases. It is argued that increasingly available digital full text research papers make it possible for citation analysis studies to go beyond what the ISI databases have directly supported and to employ more
sophisticated methods
- …
