Category: 29106-49-8

Changes in ethylene and sugar metabolism regulate flavonoid composition in climacteric and non-climacteric plums during postharvest storage was written by Farcuh, Macarena;Tajima, Hiromi;Lerno, Larry A.;Blumwald, Eduardo. And the article was included in Food Chemistry: Molecular Sciences in 2022.Recommanded Product: 29106-49-8 The following contents are mentioned in the article:

Plums are rich in flavonoids, key contributors to fruit coloration and putative health benefits. We studied the impact of changes in ethylene and sugars in flavonoid metabolism-related pathways of the climacteric Santa Rosa and its non-climacteric mutant Sweet Miriam, throughout the postharvest period. Fruits were harvested at optimal maturity, subjected to ethylene treatments, and evaluated during storage. We examined transcript profiles of structural and regulatory genes of flavonoid-related pathways and their associated metabolites in skin and flesh, integrated with multivariate analyses of ethylene and sugar metabolism Ethylene treatments were pos. correlated with anthocyanin and neg. correlated with flavonol and flavan-3-ol metabolism Sucrose and galactose were pos. associated with anthocyanin concentration, while sorbitol, fructose, glucose and minor sugars were correlated with flavonol and flavan-3-ol metabolism Our results support the notion that ethylene is playing key roles in shifting plum fruit flavonoid profiles, which are also associated with changes in fruit sugars. This study involved multiple reactions and reactants, such as (2R,2’R,3R,3’R,4R)-2,2′-Bis(3,4-dihydroxyphenyl)-[4,8′-bichromane]-3,3′,5,5′,7,7′-hexaol (cas: 29106-49-8Recommanded Product: 29106-49-8).

(2R,2’R,3R,3’R,4R)-2,2′-Bis(3,4-dihydroxyphenyl)-[4,8′-bichromane]-3,3′,5,5′,7,7′-hexaol (cas: 29106-49-8) belongs to alcohols. Under appropriate conditions, inorganic acids also react with alcohols to form esters. To form these esters, a wide variety of specialized reagents and conditions can be used. Converting an alcohol to an alkene requires removal of the hydroxyl group and a hydrogen atom on the neighbouring carbon atom. Dehydrations are most commonly carried out by warming the alcohol in the presence of a strong dehydrating acid, such as concentrated sulfuric acid.Recommanded Product: 29106-49-8

Referemce:
Alcohol – Wikipedia,
Alcohols – Chemistry LibreTexts

Multiomics analysis reveals that peach gum colouring reflects plant defense responses against pathogenic fungi was written by Liu, Jia;Zhang, Xiping;Tian, Ju;Li, Yong;Liu, Qiyue;Chen, Xiaolong;Feng, Fayun;Yu, Xiangyang;Yang, Chenye. And the article was included in Food Chemistry in 2022.Synthetic Route of C30H26O12 The following contents are mentioned in the article:

In the present study, the differences in the antioxidant capability, metabolite composition and fungal diversity in peach gum with various colors were investigated. Metabolomics revealed that peach gum comprised many small-mol. metabolites (including primary and secondary metabolites), and most polyphenols (such as flavonoids and phenolic acids) showed a significantly pos. relationship with the color deepening, total phenol content and antioxidant capability. Using fungal diversity anal., the abundance of five fungi at the genus level increased with peach gum color deepening, and these fungi demonstrated a significantly pos. relationship with two defense hormones (salicylic acid and abscisic acid) and most polyphenols (particularly flavonoids). The gummosis pathogenic fungus Botryosphaeria was among the five fungi, suggesting that peach gum coloring may reflect plant defense responses against pathogenic fungi. Addnl., the concentrations of 12 flavonoids in peach gum samples were detected based on LC-QQQ/MS, among which hesperetin, naringenin and eriodictyol were the most abundant. This study involved multiple reactions and reactants, such as (2R,2’R,3R,3’R,4R)-2,2′-Bis(3,4-dihydroxyphenyl)-[4,8′-bichromane]-3,3′,5,5′,7,7′-hexaol (cas: 29106-49-8Synthetic Route of C30H26O12).

(2R,2’R,3R,3’R,4R)-2,2′-Bis(3,4-dihydroxyphenyl)-[4,8′-bichromane]-3,3′,5,5′,7,7′-hexaol (cas: 29106-49-8) belongs to alcohols. Because alcohols are easily synthesized and easily transformed into other compounds, they serve as important intermediates in organic synthesis. Grignard and organolithium reagents are powerful tools for organic synthesis, and the most common products of their reactions are alcohols.Synthetic Route of C30H26O12

Referemce:
Alcohol – Wikipedia,
Alcohols – Chemistry LibreTexts

Incorporation of phenolic-rich ingredients from integral valorization of Isabel grape improves the nutritional, functional and sensory characteristics of probiotic goat milk yogurt was written by Silva, Francyeli Araujo;Queiroga, Rita de Cassia Ramos do Egypto;de Souza, Evandro Leite;Voss, Glenise Bierhalz;Borges, Graciele da Silva Campelo;Lima, Marcos dos Santos;Pintado, Maria Manuela Estevez;Vasconcelos, Margarida Angelica da Silva. And the article was included in Food Chemistry in 2022.Product Details of 29106-49-8 The following contents are mentioned in the article:

This study elaborated different probiotic goat milk yogurt formulations with addition of a low-calorie Isabel “Precoce” grape preparation and flour from derived solid byproducts. Physicochem. characteristics, probiotic counts, phenolic and protein/peptide mol. weight profile, antioxidant capacity (AC) and sensory acceptance of different yogurt formulations were evaluated. Yogurts with Isabel grape ingredients (IGI) had high nutritional value, distinct phenolic profile and high AC. High counts of probiotic Lactobacillus acidophilus La-05 were found in yogurts during storage. AC of yogurts with IGI increased during a simulated gastrointestinal digestion with breakdown of high mol. weight proteins and release of protein-bound phenolics. AC of yogurts with IGI should be linked to goat milk peptides and Isabel grape phenolics. Yogurts with IGI had enhanced sensory acceptance. Incorporation of Isabel grape preparation and derived byproduct flour into probiotic goat milk yogurt resulted in an added-value product with multifunctional characteristics and improved sensory characteristics. This study involved multiple reactions and reactants, such as (2R,2’R,3R,3’R,4R)-2,2′-Bis(3,4-dihydroxyphenyl)-[4,8′-bichromane]-3,3′,5,5′,7,7′-hexaol (cas: 29106-49-8Product Details of 29106-49-8).

(2R,2’R,3R,3’R,4R)-2,2′-Bis(3,4-dihydroxyphenyl)-[4,8′-bichromane]-3,3′,5,5′,7,7′-hexaol (cas: 29106-49-8) belongs to alcohols. Under appropriate conditions, inorganic acids also react with alcohols to form esters. To form these esters, a wide variety of specialized reagents and conditions can be used. Grignard and organolithium reagents are powerful tools for organic synthesis, and the most common products of their reactions are alcohols.Product Details of 29106-49-8

Referemce:
Alcohol – Wikipedia,
Alcohols – Chemistry LibreTexts

Metabolomics combined with proteomics provides a novel interpretation of the compound differences among Chinese tea cultivars (Camellia sinensis var. sinensis) with different manufacturing suitabilities was written by Chen, Dan;Sun, Zhen;Gao, Jianjian;Peng, Jiakun;Wang, Zhe;Zhao, Yanni;Lin, Zhi;Dai, Weidong. And the article was included in Food Chemistry in 2022.Recommanded Product: (2R,2’R,3R,3’R,4R)-2,2′-Bis(3,4-dihydroxyphenyl)-[4,8′-bichromane]-3,3′,5,5′,7,7′-hexaol The following contents are mentioned in the article:

Different tea cultivars differ in their manufacturing suitability. In this study, metabolomics and proteomics were applied to investigate the metabolite and protein differences in fresh leaves from 23 Chinese tea cultivars suitable for manufacturing green, white, oolong, and black teas. The combined anal. revealed 115 differential metabolites and significant differences in the biosynthesis pathways for amino acids, phenylpropanoids, flavonoids, and terpenoids, and in the peroxidases abundances among these four groups. Green tea cultivars had higher abundances of amino acids and amino acids biosynthesis-related enzymes but lower abundances of flavanols and flavonoids biosynthesis-related enzymes. Black tea cultivars presented higher abundances of flavanols, flavanol-O-glycosides, flavonoids biosynthesis-related enzymes, and peroxidases. Oolong tea cultivars showed higher abundances of enzymes involved in terpenoids biosynthesis. Our study provides a novel interpretation of the manufacturing suitability of tea cultivars from the perspective of both metabolites and proteins and will be helpful for cultivar breeding. This study involved multiple reactions and reactants, such as (2R,2’R,3R,3’R,4R)-2,2′-Bis(3,4-dihydroxyphenyl)-[4,8′-bichromane]-3,3′,5,5′,7,7′-hexaol (cas: 29106-49-8Recommanded Product: (2R,2’R,3R,3’R,4R)-2,2′-Bis(3,4-dihydroxyphenyl)-[4,8′-bichromane]-3,3′,5,5′,7,7′-hexaol).

(2R,2’R,3R,3’R,4R)-2,2′-Bis(3,4-dihydroxyphenyl)-[4,8′-bichromane]-3,3′,5,5′,7,7′-hexaol (cas: 29106-49-8) belongs to alcohols. Alkyl halides are often synthesized from alcohols, in effect substituting a halogen atom for the hydroxyl group. The most common reactions of alcohols can be classified as oxidation, dehydration, substitution, esterification, and reactions of alkoxides.Recommanded Product: (2R,2’R,3R,3’R,4R)-2,2′-Bis(3,4-dihydroxyphenyl)-[4,8′-bichromane]-3,3′,5,5′,7,7′-hexaol

Referemce:
Alcohol – Wikipedia,
Alcohols – Chemistry LibreTexts

In vitro colonic fermentation and potential prebiotic properties of pre-digested jabuticaba (Myrciaria jaboticaba (Vell.) Berg) by-products was written by Massa, Nayara Moreira Lacerda;de Oliveira, Sonia Paula Alexandrino;Rodrigues, Noadia Priscila Araujo;Menezes, Francisca Nayara Dantas Duarte;dos Santos Lima, Marcos;Magnani, Marciane;de Souza, Evandro Leite. And the article was included in Food Chemistry in 2022.Electric Literature of C30H26O12 The following contents are mentioned in the article:

Jabuticaba (Myrciaria jaboticaba (Vell.) Berg) byproducts (JB) are rich sources of dietary fiber and phenolic compounds, which can be fermented by intestinal microbiota to promote health benefits. This study evaluated the effects of a 48 h-in vitro colonic fermentation of pre-digested JB on the contents of phenolic compounds and sugars, production of organic acids, and abundance (%) of bacterial groups found as part of the human intestinal microbiota. JB reduced the pH (4.35) and promoted changes on phenolic compounds (profile and contents) and sugars, as well as production of short-chain fatty acids during the fermentation JB increased the abundance of Lactobacillus spp./Enterococcus spp. (4.32-6.25%) and Bifidobacterium spp. (4.60-10.03%) during the fermentation, and decreased the abundance of Bacteroides spp./Prevotella spp. (7.50-10.71%), Eubacterium rectale/Clostridium coccoides (1.37-3.70%), and C. histolyticum (0.91-2.30%), resulting in pos. prebiotic indexes (8.61-11.92). JB should contribute to beneficial changes in the human intestinal microbiota, with effects compatible with prebiotic ingredients. This study involved multiple reactions and reactants, such as (2R,2’R,3R,3’R,4R)-2,2′-Bis(3,4-dihydroxyphenyl)-[4,8′-bichromane]-3,3′,5,5′,7,7′-hexaol (cas: 29106-49-8Electric Literature of C30H26O12).

(2R,2’R,3R,3’R,4R)-2,2′-Bis(3,4-dihydroxyphenyl)-[4,8′-bichromane]-3,3′,5,5′,7,7′-hexaol (cas: 29106-49-8) belongs to alcohols. A strong base can deprotonate an alcohol to yield an alkoxide ion (R―O−). For example, sodamide (NaNH2), a very strong base, abstracts the hydrogen atom of an alcohol. The most common reactions of alcohols can be classified as oxidation, dehydration, substitution, esterification, and reactions of alkoxides.Electric Literature of C30H26O12

Referemce:
Alcohol – Wikipedia,
Alcohols – Chemistry LibreTexts

New insights into the influences of baking and storage on the nonvolatile compounds in oolong tea: A nontargeted and targeted metabolomics study was written by Peng, Jiakun;Dai, Weidong;Lu, Meiling;Yan, Yongquan;Zhang, Yue;Chen, Dan;Wu, Wenliang;Gao, Jianjian;Dong, Minghua;Lin, Zhi. And the article was included in Food Chemistry in 2022.HPLC of Formula: 29106-49-8 The following contents are mentioned in the article:

A nontargeted and targeted metabolomics method was applied to comprehensively investigate the influences of baking and storage on chem. constituents in fresh-, strong-, and aged-scent types of Foshou oolong teas. The contents of N-ethyl-2-pyrrolidone-substituted flavanols (EPSFs), flavone C-glycosides, gallic acid, and most lipids increased after baking and storage, while the contents of cis-flavanols, alkaloids, flavonol O-glycosides, and most amino acids decreased. Degradation, epimerization, and interaction with theanine were main pathways for the decrease in cis-flavanols. Approx. 20.7%, 12.8%, and 11.6% of epigallocatechin gallate were degraded, epimerized, and interacted with theanine after baking, resp.; 22.5% and 8.71% of epigallocatechin gallate were degraded and interacted with theanine after 10-yr storage, resp. Simulated reactions confirmed that the increases in EPSFs and apigenin C-glycosides were caused by interactions between theanine and flavanols and between apigenin aglycon and glucose, resp. This study offers novel insights into chem. changes during baking and storage of oolong tea. This study involved multiple reactions and reactants, such as (2R,2’R,3R,3’R,4R)-2,2′-Bis(3,4-dihydroxyphenyl)-[4,8′-bichromane]-3,3′,5,5′,7,7′-hexaol (cas: 29106-49-8HPLC of Formula: 29106-49-8).

(2R,2’R,3R,3’R,4R)-2,2′-Bis(3,4-dihydroxyphenyl)-[4,8′-bichromane]-3,3′,5,5′,7,7′-hexaol (cas: 29106-49-8) belongs to alcohols. Alcohols are among the most common organic compounds. They are used as sweeteners and in making perfumes, are valuable intermediates in the synthesis of other compounds, and are among the most abundantly produced organic chemicals in industry. The most common reactions of alcohols can be classified as oxidation, dehydration, substitution, esterification, and reactions of alkoxides.HPLC of Formula: 29106-49-8

Referemce:
Alcohol – Wikipedia,
Alcohols – Chemistry LibreTexts

Genetic, morphological, and chemical discrepancies between Camellia sinensis (L.) O. Kuntze and its close relatives was written by Jin, Ji-Qiang;Dai, Wei-Dong;Zhang, Chen-Yu;Lin, Zhi;Chen, Liang. And the article was included in Journal of Food Composition and Analysis in 2022.Name: (2R,2’R,3R,3’R,4R)-2,2′-Bis(3,4-dihydroxyphenyl)-[4,8′-bichromane]-3,3′,5,5′,7,7′-hexaol The following contents are mentioned in the article:

Identifying the discrepancies between cultivated tea and its wild relatives, especially in terms of their chem. compositions, is important in exploitation of specific germplasms. This study systematically investigated the phylogenetic relationships, morphol. traits, and metabolite profiles of 27 typical tea accessions. Results showed that 84,797 high-quality single nucleotide polymorphisms classified the sampled tea accessions into two groups, namely, Camellia sinensis (L.) O. Kuntze (CS) and its close relatives (CR), most of which were supported by morphol. evidence. Targeted metabolomic analyses absolutely quantified 51 characteristic metabolites. Among these metabolites, two tetragalloyled hydrolyzable tannins and four flavonol trisaccharide glycosides accumulated in low amounts in CS and CR, resp. Furthermore, the notable discrepancy in chem. composition was validated by the metabolite profiles of 114 tea accessions. Overall, this study showed the diversification of Sect. Thea plants regarding the genetic, morphol., and chem. characteristics, leading to a better understanding of wild tea plants. This study involved multiple reactions and reactants, such as (2R,2’R,3R,3’R,4R)-2,2′-Bis(3,4-dihydroxyphenyl)-[4,8′-bichromane]-3,3′,5,5′,7,7′-hexaol (cas: 29106-49-8Name: (2R,2’R,3R,3’R,4R)-2,2′-Bis(3,4-dihydroxyphenyl)-[4,8′-bichromane]-3,3′,5,5′,7,7′-hexaol).

(2R,2’R,3R,3’R,4R)-2,2′-Bis(3,4-dihydroxyphenyl)-[4,8′-bichromane]-3,3′,5,5′,7,7′-hexaol (cas: 29106-49-8) belongs to alcohols. A strong base can deprotonate an alcohol to yield an alkoxide ion (R―O−). For example, sodamide (NaNH2), a very strong base, abstracts the hydrogen atom of an alcohol. Grignard and organolithium reagents are powerful tools for organic synthesis, and the most common products of their reactions are alcohols.Name: (2R,2’R,3R,3’R,4R)-2,2′-Bis(3,4-dihydroxyphenyl)-[4,8′-bichromane]-3,3′,5,5′,7,7′-hexaol

Referemce:
Alcohol – Wikipedia,
Alcohols – Chemistry LibreTexts

Pruned vine-shoots as a new enological additive to differentiate the chemical profile of wines was written by Cebrian-Tarancon, C.;Fernandez-Roldan, F.;Sanchez-Gomez, R.;Alonso, G. L.;Salinas, M. R.. And the article was included in Food Research International in 2022.Related Products of 29106-49-8 The following contents are mentioned in the article:

For this study, Tempranillo wines were made by adding their own toasted vine-shoots (SEGs, “Shoot- Enol. – Granule”). The SEGs were added in two doses (12 and 24 g/L) at three different times (before alc. fermentation, in the middle of alc. fermentation, and after fermentations) and phenolic, volatile, and mineral composition were analyzed. Results showed a decrease in the total content of phenolic compounds but stilbenes, specifically trans-resveratrol, increased in all wines macerated with SEGs, as did total anthocyanins when these additives were added in the middle of fermentation Furthermore, the ratios related to glycosylated monomeric anthocyanins were significantly higher in wines treated with SEGs. The use of SEGs did not affect the total content of volatile compounds However, changes in terms of individual compounds resulted in an odorant series associated with SEGs, named “sweet woody”, formed by compounds such as Et vanillate, Et cinnamate, and vanillin. Finally, the mineral composition of the wines was not affected using SEGs, whereby potassium was the most abundant in all the wines. This study involved multiple reactions and reactants, such as (2R,2’R,3R,3’R,4R)-2,2′-Bis(3,4-dihydroxyphenyl)-[4,8′-bichromane]-3,3′,5,5′,7,7′-hexaol (cas: 29106-49-8Related Products of 29106-49-8).

(2R,2’R,3R,3’R,4R)-2,2′-Bis(3,4-dihydroxyphenyl)-[4,8′-bichromane]-3,3′,5,5′,7,7′-hexaol (cas: 29106-49-8) belongs to alcohols. The oxygen atom of the strongly polarized O―H bond of an alcohol pulls electron density away from the hydrogen atom. This polarized hydrogen, which bears a partial positive charge, can form a hydrogen bond with a pair of nonbonding electrons on another oxygen atom. Tertiary alcohols cannot be oxidized at all without breaking carbon-carbon bonds, whereas primary alcohols can be oxidized to aldehydes or further oxidized to carboxylic acids.Related Products of 29106-49-8

Referemce:
Alcohol – Wikipedia,
Alcohols – Chemistry LibreTexts

Nutrient composition and quality traits of dried jujube fruits in seven producing areas based on metabolomics analysis was written by Shi, Qianqian;Han, Gang;Liu, Yu;Jiang, Junjun;Jia, Yuyao;Li, Xingang. And the article was included in Food Chemistry in 2022.Product Details of 29106-49-8 The following contents are mentioned in the article:

Chinese jujube is a widely cultivated fruit of the Rhamnaceae family. However, there are few reports on the comprehensive evaluation of jujube fruit quality in the main jujube producing areas. Liquid chromatog. tandem-mass spectrometry (LC-MS/MS), principal component anal. (PCA), cluster anal., and ranking score were used to comprehensively evaluate the metabolic traits and quality of 20 dried jujube varieties in the seven main producing areas in China. A total of 29 categories of 463 metabolites were identified and detected; among them, alkaloids, amino acids, flavonoids, and lipids are the main nutrients in dried jujube fruits. An anal. of the content of metabolites in dried jujube fruits from seven producing areas showed that the difference in the fruit quality traits between the producing areas is significant, exhibiting the regional characteristics of the eastern and western regions in North China. In addition, jujube varieties HN-L-L (72 points), XJ-H-Hm (59 points), and XJ-H-Hp (59 points) with the highest scores are rich in nutrients and can be used as raw materials in the development of functional foods. This study involved multiple reactions and reactants, such as (2R,2’R,3R,3’R,4R)-2,2′-Bis(3,4-dihydroxyphenyl)-[4,8′-bichromane]-3,3′,5,5′,7,7′-hexaol (cas: 29106-49-8Product Details of 29106-49-8).

(2R,2’R,3R,3’R,4R)-2,2′-Bis(3,4-dihydroxyphenyl)-[4,8′-bichromane]-3,3′,5,5′,7,7′-hexaol (cas: 29106-49-8) belongs to alcohols. The oxygen atom of the strongly polarized O―H bond of an alcohol pulls electron density away from the hydrogen atom. This polarized hydrogen, which bears a partial positive charge, can form a hydrogen bond with a pair of nonbonding electrons on another oxygen atom. Grignard and organolithium reagents are powerful tools for organic synthesis, and the most common products of their reactions are alcohols.Product Details of 29106-49-8

Referemce:
Alcohol – Wikipedia,
Alcohols – Chemistry LibreTexts

Ultrasound-assisted adsorption/desorption of jujube peel flavonoids using macroporous resins was written by Shen, Dongbei;Labreche, Faiza;Wu, Caie;Fan, Gongjian;Li, Tingting;Dou, Jinfeng;Zhu, Jinpeng. And the article was included in Food Chemistry in 2022.Safety of (2R,2’R,3R,3’R,4R)-2,2′-Bis(3,4-dihydroxyphenyl)-[4,8′-bichromane]-3,3′,5,5′,7,7′-hexaol The following contents are mentioned in the article:

The work explored the process of ultrasound-assisted adsorption/desorption to efficiently purify jujube peel flavonoids (JPFs) using macroporous resins (MRs). The impact of ultrasound power and temperature on the adsorption/desorption features of JPFs on MRs were studied. The maximum adsorption (80.21 ± 2.11 mg/g) /desorption (76.22 ± 1.68 mg/g) capacity of total flavonoids content were obtained. The pseudo-second-order kinetic and Freundlich isotherm models better described the whole process of ultrasound-assisted adsorption. The adsorption process was spontaneous, phys., and dominated by multilinear intraparticle diffusion. Ultrasound mainly enhanced the adsorption capacity by strengthening the formation of hydrogen bonds and increasing the surface roughness of MRs. Besides, the principal individual flavonoid ((+)-Catechin, (-)-Epicatechin, Rutin, Quercetin-3-O-robinobioside) content of JPFs in ultrasound treatment was 2-3 times that of shaking treatment, and biol. activities were significantly increased. Overall, as a low-cost green technol., ultrasound can improve the properties of MRs and better purify JPFs. This study involved multiple reactions and reactants, such as (2R,2’R,3R,3’R,4R)-2,2′-Bis(3,4-dihydroxyphenyl)-[4,8′-bichromane]-3,3′,5,5′,7,7′-hexaol (cas: 29106-49-8Safety of (2R,2’R,3R,3’R,4R)-2,2′-Bis(3,4-dihydroxyphenyl)-[4,8′-bichromane]-3,3′,5,5′,7,7′-hexaol).

(2R,2’R,3R,3’R,4R)-2,2′-Bis(3,4-dihydroxyphenyl)-[4,8′-bichromane]-3,3′,5,5′,7,7′-hexaol (cas: 29106-49-8) belongs to alcohols. The oxygen atom of the strongly polarized O―H bond of an alcohol pulls electron density away from the hydrogen atom. This polarized hydrogen, which bears a partial positive charge, can form a hydrogen bond with a pair of nonbonding electrons on another oxygen atom. A multistep synthesis may use Grignard-like reactions to form an alcohol with the desired carbon structure, followed by reactions to convert the hydroxyl group of the alcohol to the desired functionality.Safety of (2R,2’R,3R,3’R,4R)-2,2′-Bis(3,4-dihydroxyphenyl)-[4,8′-bichromane]-3,3′,5,5′,7,7′-hexaol

Referemce:
Alcohol – Wikipedia,
Alcohols – Chemistry LibreTexts