Scholarly Work - Health & Human Development

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    White and Green Teas (Camellia sinensis var. sinensis): Variation in Phenolic, Methylxanthine, and Antioxidant Profiles
    (2010-08) Unachukwu, Uchenna J.; Ahmed, Selena; Kavalier, Adam; Lyles, James T.; Kennelly, Edward J.
    Recent investigations have associated white teas with anti‐carcinogenic, immune‐boosting, and antioxidative properties that may impact human health in a manner comparable to green teas. An in‐depth chemical analysis of white tea types was conducted to quantify polyphenols and antioxidant potential of 8 commercially available white teas, and compare them to green tea. Extraction and HPLC protocols were optimized and validated for the quantification of 9 phenolic and 3 methylxanthine compounds to examine inter‐ and intra‐variation in white and green tea types and subtypes. A sampling strategy was devised to assess various subtypes procured from different commercial sources. Variation in antioxidant activity and total phenolic content (TPC) of both tea types was further assessed by the 1‐1‐diphenyl‐2‐picrylhydrazyl (DPPH) and Folin–Ciocalteau (F–C) assays, respectively. Total catechin content (TCC) for white teas ranged widely from 14.40 to 369.60 mg/g of dry plant material for water extracts and 47.16 to 163.94 mg/g for methanol extracts. TCC for green teas also ranged more than 10‐fold, from 21.38 to 228.20 mg/g of dry plant material for water extracts and 32.23 to 141.24 mg/g for methanol extracts. These findings indicate that statements suggesting a hierarchical order of catechin content among tea types are inconclusive and should be made with attention to a sampling strategy that specifies the tea subtype and its source. Certain white teas have comparable quantities of total catechins to some green teas, but lesser antioxidant capacity, suggesting that white teas have fewer non‐catechin antioxidants present.
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    Pu-erh Tea Tasting in Yunnan, China: Correlation of Drinkers’ Perceptions to Phytochemistry.
    (2010-10) Ahmed, Selena; Unachukwu, Uchenna J.; Stepp, John R.; Peters, Charles M.; Long, Chunlin; Kennelly, Edward J.
    Aim of the study: Pu-erh (or pu’er) tea tasting is a social practice that emphasizes shared sensory experience, wellbeing, and alertness. The present study examines how variable production and preparation practices of pu-erh tea affect drinkers’ perceptions, phytochemical profiles, and anti-oxidant activity. Materials and methods: One hundred semi-structured interviews were conducted in Yunnan Province to understand the cultural and environmental context of pu-erh tea tasting. The gong fu cha dao (‘way of tea’ with ‘effort,’ ‘work,’ or ‘skill’) method of brewing tea through multiple infusions was employed to evaluate green and black pu-erh samples from smallholder agro-forests and terrace plantations. Ranking interviews, High Performance Liquid Chromatography (HPLC), and the 1-1-diphenyl-2-picrylhydrazyl (DPPH) assay were conducted to characterize color and taste profiles, Total Catechin Content (TCC), Total Methylxanthine Content (TMC), and free radical scavenging capacity (IC50). Results: Significant variation was found among pu-erh samples based on: (1) agro-ecosystem mode of production by TCC (P < 0.0001) and TMC (P < 0.0265), (2) processing method for TCC (P < 0.0001), TMC (P < 0.0027), and free radical scavenging capacity (P < 0.0001), (3) infusion sequence for TMC (P < 0.0013), (4) taste rankings for TCC (P < 0.0001), TMC (P < 0.0001), and IC50 (P < 0.0059) and, (5) color rankings for TMC (P < 0.0009) and IC50 (P < 0.0001). Samples rated as bitter and bitter-sweet contained the greatest TCC and free radical scavenging capacity. Conclusions: This research demonstrated that production environment, processing methods, and infusion sequence in preparing tea are related to the phytochemical profile, free radical scavenging activity, and flavor of tea. Findings contribute to the ethnomedical literature by supporting previous studies that have hypothesized that the taste of plants, particularly bitterness, may guide societies in the search for medicinal plants and beneficial phytochemicals.
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    The Role of Montane Forests for Indigenous Dongba Papermaking in the Naxi Highlands of Northwest Yunnan, China. Mountain Research and Development.
    (2011-11) Yang, Lixin; Stepp, John R.; Ahmed, Selena; Pei, Shengji; Xue, Dayuan
    China's rapid economic development is influencing cultural practices and natural resource management in indigenous mountain communities throughout the country. Numerous studies have documented loss and change of cultural practices and environmental degradation in indigenous communities with the expansion of roads, markets, tourism, and other infrastructure development. The present study focuses on papermaking, a socioecological practice that began in China, as a case study to examine the influence of development on cultural practices and natural resource management. The Naxi are an indigenous people who primarily inhabit the mountains of the eastern Himalaya in China's northwest Yunnan province. The Naxi people are unique in that they have the last remaining pictographic writing system in the world. The Naxi pictographic script is customarily learned and mastered by shaman priests known as Dongba (Dto'mba) who transmit their knowledge to their sons. Approximately 300,000 Naxi live in this area. The pictographic system is transmitted on paper sourced from montane forest resources, primarily Wisktroemia delavayi. This cultural tradition almost disappeared during the Cultural Revolution in China during the 1960s and 1970s but has recently seen a revival. Research involved both ethnographic interviews and ecological sampling. Semistructured interviews were conducted with 100 informants between 2002–2011 to understand the management and use of W. delavayi for Dongba papermaking and the impact of market integration on papermaking. Sample plots were surveyed for floristic composition and structure in the 3 vegetation types where W. delavayi grows. Density, height, diameter, and number of branches of W. delavayiplants were recorded within each plot. Ecological importance values were calculated based on relative density, relative dominance, and relative frequency to determine the habitat where W. delavayidemonstrates the greatest growth. Additional plots were surveyed to understand the regeneration of W. delavayi after the local harvest cycle.
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    Commercial Teas Highlight Plant DNA Barcode Identification Successes and Obstacles.
    (2011-07) Stoeckle, Mark Y.; Gamble, Catherine C.; Kirpekar, Rohan; Young, Grace; Ahmed, Selena; Little, Damon P.
    Appearance does not easily identify the dried plant fragments used to prepare teas to species. Here we test recovery of standard DNA barcodes for land plants from a large array of commercial tea products and analyze their performance in identifying tea constituents using existing databases. Most (90%) of 146 tea products yielded rbcL or matKbarcodes using a standard protocol. Matching DNA identifications to listed ingredients was limited by incomplete databases for the two markers, shared or nearly identical barcodes among some species, and lack of standard common names for plant species. About 1/3 of herbal teas generated DNA identifications not found on labels. Broad scale adoption of plant DNA barcoding may require algorithms that place search results in context of standard plant names and character-based keys for distinguishing closely-related species. Demonstrating the importance of accessible plant barcoding, our findings indicate unlisted ingredients are common in herbal teas.
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    Increased Market Integration, Value, and Ecological Knowledge of Tea Agro-forests in the Akha Highlands of Southwest China.
    (2010) Ahmed, Selena; Stepp, John R.; Toleno, Robban A. J.; Peters, Charles M.
    This study assesses the persistence and change of traditional land use patterns and ecological knowledge in response to expanded commercialization of tea (Camellia sinensis var. assamica (L.) Kuntze Theaceae in an indigenous Akha (Hani) community in the midlevel montane forests of southwest Yunnan, China. Surveys were conducted in 2005 and 2008, over a period corresponding to a regional tea market boom and bust cycle, to compare the valuation smallholders attribute to land use types and to determine the role that value systems play in shaping environmental behavior and knowledge. At the community level, increased market integration of tea agroforests is associated with reconfiguration of land use, intensified management, reorganization of labor structures, and generation of knowledge on tea resources. Akha have tapped into customary resources and forged new social networks with tea industry agents to take advantage of emerging market opportunities. They have resisted state reforms calling for the cultivation of high-intensity plantations and introduced cultivars. Consequently, they have benefited from price premiums through niche market networks for tea sourced from agroforests and proprietary landraces not available to other communities disempowered by market cycles. Subsistence agriculture, home gardening, and foraging persist for food security despite tea wealth. However, as traditional values are reoriented toward market-based ideologies, the community may risk a breakdown of the social institutions that support sustainability.
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