Diversity of Plant Colorant Species in a Biodiversity Hotspot in Northern Thailand

Abstract

Growing concerns regarding health and eco-safety have led to a resurgence in the recognition of natural products. Although plant colorants are often mentioned in ethnobotanical studies in northern Thailand, they have not been comprehensively examined. This study aims to (i) investigate the colorant plants used by ethnic minorities in northern Thailand and (ii) compare colorant plants used among the groups in northern Thailand with other regions worldwide. Data on colorant plants used by ten ethnic groups across 142 villages in northern Thailand were extracted in a systematic review of 42 published references. The importance of the colorant plant species was evaluated using the ethnobotanical index “use value” (UV), and the homogeneity of knowledge was assessed using the “information consensus factor” (ICF). The similarity of colorant plants used among the ethnic minority groups and beyond was evaluated using Jaccard’s index. The 42 published references included information about 104 colorant plant species belonging to 85 genera and 43 families from seven provinces in northern Thailand. This represents nearly half of the 212 colorant plant species reported across all 72 provinces in Thailand. The most important species were Strobilanthes cusia and Morinda angustifolia, which are sources of blue and red colors. Fabaceae, Rubiaceae, and Lamiaceae were the plant families with most species used as colorants. The colorant plant species yielded ten different color shades, with blue being the most prevalent. The Jaccard’s index varied from 0 to 0.27 among the northern Thai ethnic minorities and from 0 to 0.13 for regions outside of northern Thailand. The regions located closest to northern Thailand exhibited the highest degree of similarity. This study provides valuable insights into the traditional knowledge and usage of dye plants in northern Thailand, contributing to preserving the cultural heritage and providing basic knowledge for the sustainable use of natural colorants for modern applications.