Island blues: indigenous knowledge of indigo-yielding plant species used by Hainan Miao and Li dyers on Hainan Island, China

Indigoferajintongpenensis (Fabaceae, Papilionoideae, Indigofereae), a new species from Yunnan, southwest China

Indigoferajintongpenensis, a new species of the subfamily Papilionoideae of Fabaceae, is described and illustrated from Yunnan, southwest China. The new species is characterised by having a prostrate habit, flexible stems and branches, as well as spreading, sub-basifixed, asymmetrically 2-branched trichomes covering the entire plant, discoid calyx, and racemose inflorescences 6-8-flowered, short, 1-2 (-3.5) cm in length, apparently shorter than the leaf. A distribution map and comparison of morphological diagnostic characters with its morphologically similar species are provided. Additionally, a preliminary conservation assessment of I.jintongpenensis is proposed following IUCN criteria.

"Purplish Blue" or "Greenish Grey"? Indigo Qualities and Extraction Yields from Six Species

Indigo quality is determined by its indigotin content. Another quality indicator is colour. For an evaluation of species, indigo samples from Indigofera tinctoria, Indigofera suffruticosa, Indigofera arrecta, Persicaria tinctoria, Strobilanthes cusia and Wrightia laevis cultivated in Austria and China were visually classified and analysed spectrophotometrically and using a L*a*b* measuring device. In addition to a standardised hot-extraction method without lime, some samples were extracted simulating traditional methods at ambient temperatures using lime. The highest indigotin contents were achieved with Indigofera arrecta (55%, Austria) and Strobilanthes cusia (56%, China). There were no statistically significant differences between the indigo extraction yields of the species cultivated in Austria, but Indigofera arrecta and Persicaria tinctoria had statistically significantly higher indigotin extraction yields than Indigofera tinctoria and Indigofera suffruticosa. From the species extracted in China, Strobilanthes cusia showed higher values in all parameters than Indigofera tinctoria, Indigofera suffruticosa and Wrightia laevis. Compared with the standardised method, the method simulating local practice yielded more indigo but had a lower indigotin content; the indigotin extraction yields did not differ greatly. L*a*b* values enabled precise estimations of the indigotin content, making it an interesting option for quality control, as inexpensive, easy-to-handle L*a*b* measuring instruments have become available.

Indigo production goes green: a review on opportunities and challenges of fermentative production

Indigo is a widely used dye in various industries, such as textile, cosmetics, and food. However, traditional methods of indigo extraction and processing are associated with environmental and economic challenges. Fermentative production of indigo using microbial strains has emerged as a promising alternative that offers sustainability and cost-effectiveness. This review article provides a critical overview of microbial diversity, metabolic pathways, fermentation strategies, and genetic engineering approaches for fermentative indigo production. The advantages and limitations of different indigo production systems and a critique of the current understanding of indigo biosynthesis are discussed. Finally, the potential application of indigo in other sectors is also discussed. Overall, fermentative production of indigo offers a sustainable and bio-based alternative to synthetic methods and has the potential to contribute to the development of sustainable and circular biomanufacturing.

Phylogenomics and plastome evolution of Indigofera (Fabaceae)

Introduction

Indigofera L. is the third largest genus in Fabaceae and includes economically important species that are used for indigo dye-producing, medicinal, ornamental, and soil and water conservation. The genus is taxonomically difficult due to the high level of overlap in morphological characters of interspecies, fewer reliability states for classification, and extensive adaptive evolution. Previous characteristic-based taxonomy and nuclear ITS-based phylogenies have contributed to our understanding of Indigofera taxonomy and evolution. However, the lack of chloroplast genomic resources limits our comprehensive understanding of the phylogenetic relationships and evolutionary processes of Indigofera.

Methods

Here, we newly assembled 18 chloroplast genomes of Indigofera. We performed a series of analyses of genome structure, nucleotide diversity, phylogenetic analysis, species pairwise Ka/Ks ratios, and positive selection analysis by combining with allied species in Papilionoideae.

Results and discussion

The chloroplast genomes of Indigofera exhibited highly conserved structures and ranged in size from 157,918 to 160,040 bp, containing 83 protein-coding genes, 37 tRNA genes, and eight rRNA genes. Thirteen highly variable regions were identified, of which trnK-rbcL, ndhF-trnL, and ycf1 were considered as candidate DNA barcodes for species identification of Indigofera. Phylogenetic analysis using maximum likelihood (ML) and Bayesian inference (BI) methods based on complete chloroplast genome and protein-coding genes (PCGs) generated a well-resolved phylogeny of Indigofera and allied species. Indigofera monophyly was strongly supported, and four monophyletic lineages (i.e., the Pantropical, East Asian, Tethyan, and Palaeotropical clades) were resolved within the genus. The species pairwise Ka/Ks ratios showed values lower than 1, and 13 genes with significant posterior probabilities for codon sites were identified in the positive selection analysis using the branch-site model, eight of which were associated with photosynthesis. Positive selection of accD suggested that Indigofera species have experienced adaptive evolution to selection pressures imposed by their herbivores and pathogens. Our study provided insight into the structural variation of chloroplast genomes, phylogenetic relationships, and adaptive evolution in Indigofera. These results will facilitate future studies on species identification, interspecific and intraspecific delimitation, adaptive evolution, and the phylogenetic relationships of the genus Indigofera.

Indigofera tinctoria L. leaf powder promotes initiation of indigo reduction by inducing of rapid transition of the microbial community

Water-insoluble indigo is solubilized by the reducing action of microorganisms which occurs during fermentation. In natural indigo fermentation, composted leaves of Polygonum tinctorium L. (sukumo) are the raw material that has been used as both the indigo source and the bacterial inoculum. Ideally, indigo reduction occurs shortly after preparation of the fermentation vat. The time-to-reduction depends on the quality of the sukumo and the methods for preparation and management of the fermentation batch. We estimated the effect of adding Indigofera tinctoria L. leaf powder (LP) to indigo fermentation in two fermentations originally exhibiting either rapid or slow time-to-reduction (T-sukumo and D-sukumo, respectively). Alkalihalobacillus spp. (97.7%–98.4% similarities with Alkalihalobacillus macyae) were observed only in the LP-added T-sukumo fermentation liquor. They appeared from day 1 (0.7%) and increased to 24.4% on day 6, and their presence was related to indigo reduction. Differences in functional ratio between LP-added and its control batches revealed enhancement of pathways related to reconstitution of cellular functions and substrate metabolisms, to all of which Alkalihalobacillus spp. contributed intensively. In D-sukumo batch, appearance of bacteria necessary to initiate indigo reduction (principally Anaerobacillus/Polygonibacillus) was comparatively slower. LP promotes earlier indigo reduction in both T- and D-sukumo-based batches, owing to its promotion of microbiota transition. The effect of the LP was intensified from day 1 to day 2 in both sukumo using batches according to the assumed function of the microbiota. The initial effect of LP on the T-sukumo batches was more intense than that in the D-sukumo batches and was continued until day 3, while the duration in the T-sukumo batches was continued until day 5. Based on these observations, we propose that the LP functions through its phytochemicals that eliminate oxygen, stimulate the microbiota, and accelerate its transitional changes toward a suitable function that opens the pathway for the extracellular electron transfer using carbohydrates as a substrate.

Indigo-A New Tribological Substance Class for Non-Toxic and Ecological Gliding Surfaces on Ice, Snow, and Water

The biogenic substance E-indigo can form supramolecular, hydrophobic structures using self-organization. These structures show a low coefficient of friction as a gliding layer against polar surfaces. The formation of primary particles with platelet morphology based on hydrogen-bonded E-indigo molecules is ideal to produce the gliding layer. Structures with excellent gliding properties can be achieved by means of directed friction and high pressure, as well as through tempering. The resulting hard, thin gliding layer of E-indigo does not easily absorb dirt and, thus, prevents a rapid increase in friction. Field tests on snow, with cross-country skis, have shown promising results in comparison to fluorinated and non-fluorinated waxes. Based on quantitative structure–activity relationship (QSAR) data for E-indigo, and its isomers and tautomers, it has been demonstrated that both the application and abrasion of the thin indigo layers are harmless to health, and are ecologically benign and, therefore, sustainable.

Indigofera tinctoria leaf powder as a promising additive to improve indigo fermentation prepared with sukumo (composted Polygonum tinctorium leaves)

Being insoluble in the oxidize form, indigo dye must be solubilized by reduction for it to penetrate textile. One of the procedures is the reduction by natural bacterial fermentation. Sukumo, composted leaves of Polygonum tinctorium, is a natural source of indigo in Japan. Although sukumo has an intrinsic bacterial seed, the onset of indigo reduction with this material may vary greatly. Certain additives improve indigo fermentation. Here, we studied the effects of Indigofera tinctoria leaf powder (LP) on the initiation of indigo reduction, bacterial community, redox potential (ORP), and dyeing intensity in the initial stages and in aged fermentation fluids prepared with sukumo. I. tinctoria LP markedly decreased ORP at day 1 and stabilised it during early fermentation. These effects could be explained by the phytochemicals present in I. tinctoria LP that act as oxygen scavengers and electron mediators. Using next generation sequencing results, we observed differences in the bacterial community in sukumo fermentation treated with I. tinctoria LP, which was not influenced by the bacterial community in I. tinctoria LP per se. The concomitant decrease in Bacillaceae and increase in Proteinivoraceae at the onset of fermentation, increase in the ratio of facultative to obligate anaerobes (F/O ratio), or the total abundance of facultative anaerobes (F) or obligate anaerobes (O) (designated F + O) are vital for the initiation and maintenance of indigo reduction. Hence, I. tinctoria LP improved early indigo reduction by decreasing the ORP and hasten the appropriate transitions in the bacterial community in sukumo fermentation.

Analysis of bacterial flora of indigo fermentation fluids utilizing composted indigo leaves (sukumo) and indigo extracted from plants (Ryukyu-ai and Indian indigo)

Indigo is a fabric dye that requires reduction by microbial activity or chemical reagents to render it soluble in water. Sources of indigo for fermentation are primarily divided into composted indigo-containing plants and indigo extracted from plants. To elucidate the factors responsible for bacterial diversity, and for sustaining reduced state of indigo in different preparations, this study assessed fermentation-derived fluids using composted plant leaves, sukumo, and extracted indigo (Ryukyu-ai paste, and Indian indigo cake) prepared using different procedures. Regardless of the indigo source, obligate anaerobic bacteria, including the families Proteinivoraceae and Tissierellaceae, predominate (16.9-46.1%), suggesting their high affinity for this fermentation ecosystem (hyperalkaline and low redox potential). Moreover, bacterial communities in sukumo fermentations are more diverse than those from indigo extracts with the diversity tending to increase based on the fermentation period. Our results further suggest that the microbiota composition in sukumo fermentation is associated with the various bacterial nutrients derived from sukumo, including seed microorganisms. In addition, the debris derived from sukumo can reduce the pH stress experienced by the microorganisms. Further, regardless of 5.4 years difference in the fermentation age, the bacterial flora in two Ryukyu-ai batches exhibit similar features with low microbial diversities. The uniformity of the nutrient, along with the simple, yet strong, bacterial network in Ryukyu-ai fluids may be responsible for the stable bacterial flora composition. Taken together, these results indicate that the microbiota in indigo fermentation is highly influenced by the seed culture, the nutrient derived from raw materials, and the fermentation conditions.

Electrochemical Fingerprint Biosensor for Natural Indigo Dye Yielding Plants Analysis

Indigo is a plant dye that has been used as an important dye by various ancient civilizations throughout history. Today, due to environmental and health concerns, plant indigo is re-entering the market. Strobilanthes cusia (Nees) Kuntze is the most widely used species in China for indigo preparation. However, other species under Strobilanthes have a similar feature. In this work, 12 Strobilanthes spp. were analyzed using electrochemical fingerprinting technology. Depending on their electrochemically active molecules, they can be quickly identified by fingerprinting. In addition, the fingerprint obtained under different conditions can be used to produce scattered patter and heatmap. These patterns make plant identification more convenient. Since the electrochemically active components in plants reflect the differences at the gene level to some extent, the obtained electrochemical fingerprints are further used for the discussion of phylogenetics.

Quality blues: traditional knowledge used for natural indigo identification in southern China

BACKGROUND

As one of the oldest traditional dyes, people worldwide have used natural indigo for centuries. Local people have unique knowledge about indigo identification, which is crucial for indigo quality control and determining the dyeing effects. However, such traditional knowledge is rarely documented and explained. Therefore, the aims of this study were to document and assess the traditional knowledge used by local people when identifying natural indigo paste as well as quantitatively explore the characteristics and material basis of such traditional knowledge.

METHOD

Three field surveys were conducted between 2019 and 2020. A total of 283 traditional indigo-paste artisans were interviewed in Guizhou, Yunnan, and Fujian Provinces. The frequency of citation, mention index, and fidelity level of each indigo-paste quality criterion were calculated to determine the most commonly used, recognized, and important quality criteria. To explore the characteristics and material basis of the traditional knowledge, we analyzed 21 indigo-paste samples using high-performance liquid chromatography with diode-array detection (HPLC-DAD), pH, and particle size analyses.

RESULTS

Local people possess unique knowledge to identify natural indigo. Based on this knowledge accumulated over thousands of years, four criteria (color, taste, touch, and dyeing ability) were chosen by local people, and using these criteria, nature indigo was divided into five quality grades. The best quality indigo paste was judged according to the following folk criteria: dark blue in color with a purple-red luster; smooth and difficult to wipe off; having a sweet, bitter or spicy taste; and easy cloth dyeing. Additionally, the higher the contents of indigo and indirubin-especially indirubin-the better is the quality of the indigo paste. Within the pH range of 9-12, high-quality indigo-paste was more acidic. There was no significant relationship between particle size and quality.

CONCLUSION

The ancient methods used by local people for identifying natural indigo are comprehensive and unique. By documenting the various folk quality criteria and conducting quantitative analyses, this study revealed the importance of indirubin and pH for assessing the quality of indigo paste. These findings differ from existing quality standards for synthetic indigo. Amid rapid modernization, traditional knowledge remains invaluable as a world heritage of humanity that warrants preservation.

Strobilanthes cusia (Nees) Kuntze, a multifunctional traditional Chinese medicinal plant, and its herbal medicines: A comprehensive review

ETHNOPHARMACOLOGICAL RELEVANCE

Strobilanthes cusia (Nees) Kuntze (SCK, Malan), a traditional Chinese medicinal plant, has long applied to detoxification, defervescence, detumescence and antiphlogosis. "Southern Banlangen" (Rhizoma et Radix Baphicacanthis Cusiae, RRBC), root and rhizome of SCK, is widely used for treatment of many epidemic diseases. Malanye (Southern Daqingye), stem and leaf of SCK, is an antipyretic-alexipharmic drug frequently-used in southern China. Qingdai (Indigo Naturalis, IN), a processed product of SCK, is always applied to dermatoses in the folk.

AIM OF THE REVIEW

In order to elucidate the historical uses, recent advances and pharmaceutical prospects of SCK, we summarized roundly in aspects of history, processing method, chemical constitution, quality control, pharmacological activity and toxicity. Some deficiencies in current studies and research directions in the future are also discussed. This is the first comprehensive review of SCK and its herbal medicines, which may be of some help for further research.

METHODOLOGY

Comprehensive analysis was conducted on the basis of academic papers, pharmaceutical monographs, ancient medicinal works, and drug standards of China. All available information on SCK and its herbal medicines was collected by using the keywords such as "Strobilanthes cusia", "Southern Banlangen", "indirubin", "tryptanthrin" through different electronic databases including NCBI Pubmed, Google Scholar, Chinese National Knowledge Infrastructure and so on. Pharmacopoeia of China and some ancient works were obtained from National Digital Library of China.

RESULT

Medicinal uses of SCK were already described by famous ancient researchers. Because of vague description, plant species in some works cannot be confirmed. Literature demonstrated that multiple components including total 36 alkaloids and 35 glycosides, the main bioactive components of SCK, were found in SCK and its herbal medicines. Modern studies indicated that SCK and some of its components had multiple pharmacological effects including resistance to cancer, remission of inflammation, suppression of microorganisms, relief of dermatoses, and so on. However, studies on pharmacology, pharmacokinetics, and quality control are still not enough.

CONCLUSION

A number of reports suggested that SCK and its processed medicines could be promising drug candidates for multiple diseases especially promyelocytic leukemia, ulcerative colitis (UC) and psoriasis. However, bioactive activities of most components, especially glycosides should still be explored further. It is crucial to elucidate the in-depth molecular mechanisms, and pharmacokinetic characteristics of main components in those herbal medicines. Moreover, to ensure the effectiveness of clinical medication, future studies should undoubtedly give the priority to clarifying the effective compositions of SCK, and then a measurement standard of those indicators should be protocolled to establish a comprehensive quality evaluation mode.

Blue genome: chromosome-scale genome reveals the evolutionary and molecular basis of indigo biosynthesis in Strobilanthes cusia

Natural plant dyes have been developed and used across many traditional societies worldwide. The blue pigment indigo has seen widespread usage across South America, Egypt, Europe, India and China for thousands of years, mainly extracted from indigo-rich plants. The utilization and genetic engineering of indigo in industries and ethnobotanical studies on the effects of cultural selection on plant domestication are limited due to lack of relevant genetic and genomic information of dye plants. Strobilanthes cusia (Acanthaceae) is a typical indigo-rich plant important to diverse ethnic cultures in many regions of Asia. Here we present a chromosome-scale genome for S. cusia with a genome size of approximately 865 Mb. About 79% of the sequences were identified as repetitive sequences and 32 148 protein-coding genes were annotated. Metabolic analysis showed that the main indigoid pigments (indican, indigo and indirubin) were mainly synthesized in the leaves and stems of S. cusia. Transcriptomic analysis revealed that the expression level of genes encoding metabolic enzymes such as monooxygenase, uridine diphosphate-glycosyltransferase and β-glucosidase were significantly changed in leaves and stems compared with root tissues, implying their participation in indigo biosynthesis. We found that several gene families involved in indigo biosynthesis had undergone an expansion in number, with functional differentiation likely facilitating indigo biosynthesis in S. cusia. This study provides insight into the physiological and molecular bases of indigo biosynthesis, as well as providing genomic data that provide the basis for further study of S. cusia cultivation by Asia's traditional textile producers.

Ethnobotanical study on plants used for traditional beekeeping by Dulong people in Yunnan, China

BACKGROUND

The Dulong (Drung) people have used plant materials in traditional beekeeping for many decades. However, there are few studies on the plants used in traditional beekeeping. Furthermore, traditional ecological knowledge (TEK) associated with beekeeping is still poorly understood. TEK and plants associated with beekeeping play an important role in the conservation of native bees and the development of beekeeping. It is therefore very urgent to investigate, record, and study the plants and TEK of Dulong beekeeping.

METHODS

Fieldwork was conducted in the Dulong community of Gongshan County, Yunnan Province, China. Six Dulong villages were investigated. Ethnobotanical methods such as free listing, semi-structured interviews, participatory observation, and key informant interviews were used to collect data. A total of 42 Dulong respondents provided information about plants used in traditional beekeeping. TEK related to traditional beekeeping plants was documented. Citation frequency, abundance, and preference ranking of log beehive plant species were used to identify plant resources that are "easier to obtain" and "more preferred."

RESULTS

There are two general methods of traditional Dulong beekeeping: living tree beekeeping and log beehive beekeeping. The investigation revealed that 38 species (in 19 families), including 30 tree species, 5 bamboo species, 2 herbaceous species, and 1 liana species, are used in traditional Dulong beekeeping. Different plant parts are used for different purposes. Twenty-seven tree species are used to make log beehives. Species from the family Pinaceae and Fagaceae are the most frequently represented. Seven of the most commonly reported species used to build log beehives were scored by ten beekeepers. Based on this scoring, the beekeepers' most preferred species for making log beehives are Alnus nepalensis, Pinus yunnanensis, and Juglans regia.

CONCLUSION

The Dulong people have used various plants for traditional beekeeping and have accumulated rich TEK associated with apiculture. Future research will include a nutritive components analysis of honey from traditional Dulong beekeeping and an ethnobotanical investigation of melliferous species used in traditional Dulong apicultural systems. The application of plants and TEK associated with beekeeping is important for improving livelihoods in local communities, conserving biocultural diversity, and protecting the eco-environment of the Dulongjiang area.