Pathological Analyses Department, College of Science, University of Thi Qar, Nasiriyah, Iraq.
Medical Microbiology Branch, College of Medicine, University of Basra, Basra, Iraq.
Biotech Histochem. 2022 Oct;97(7):480-489. doi: 10.1080/10520295.2022.2113142. Epub 2022 Aug 24.
Interest is increasing in certain parts of the world in replacing synthetic dyes with dyes from natural sources, particularly from plants. Although textile dyers have used various groups of natural dyes, microscopists generally have restricted their use to anthocyanins. Recently, however, another class of plant-based dyes has found some favor, the betacyanins. Betacyanins are a group of red and violet betalain dyes found only in certain plants of the order Caryophyalles and in Basidiomycetes mushrooms. Although the chemical structures of betacyanins are known, little use has been made of that information to understand or predict their behavior with biomedical specimens. We investigated two common, widely distributed betacyanin-containing plants, edible beets () and wild pokeweed (). Aqueous alcoholic extracts were made from beet root and pokeweed berries, adjusted to pH 4.1 or 5.3 and used together with Harris' hematoxylin to stain histological sections. We used a methanolic extract of pokeweed berries, pH 3.0, to stain cultured mycological specimens. Both extracts produced satisfactory staining that was equivalent to that of eosin Y, although the colors were more muted with the beet root extract. Epithelial cytoplasm, muscle, collagen and erythrocytes were well demonstrated. Betanin is the predominant component of beet root extract; it possesses one delocalized positive charge and three carboxylic acid substituents. The dyes are weak acids and the carboxylate anions are more diffuse than for eosin Y; this produces weaker bonding to tissue cations. The principal colored component of pokeweed berries, prebetanin, possesses a sulfonic acid group as well as carboxylic acids, which favors acid dyeing and more intense coloration. Both dyes show potential for hydrogen bonding and to a much lesser extent for some types of van der Waals forces. Complex formation with metals such as aluminum to create a nuclear stain is not likely with beet root dyes nor is it possible with pokeweed dyes. Betacyanins are suitable for staining microscopy preparations in place of other red acid dyes such as eosin. Of the two dyes tested here, prebetanin from pokeweed berries was superior to betanin from red beet roots. These berries are widely distributed and readily collected; the extraction procedure is simple and does not require expensive solvents.
人们对用天然染料替代合成染料越来越感兴趣，尤其是从植物中提取的天然染料。尽管纺织染料已经使用了各种天然染料，但显微镜专家通常只将注意力集中在花色苷上。然而，最近，另一类植物染料受到了一些关注，即甜菜红素。甜菜红素是一类仅存在于石竹目某些植物和担子菌蘑菇中的红色和紫色甜菜碱类染料。尽管甜菜红素的化学结构是已知的，但很少有利用这些信息来了解或预测它们在生物医学标本中的行为。我们研究了两种常见的、分布广泛的含甜菜红素植物，食用甜菜（）和野生龙葵（）。从甜菜根和龙葵浆果中提取水醇提取物，将其 pH 值调节为 4.1 或 5.3，并与 Harris 苏木精一起用于染色组织切片。我们使用 pH 值为 3.0 的龙葵浆果甲醇提取物来染色培养的真菌标本。两种提取物都产生了令人满意的染色效果，与曙红 Y 相当，尽管甜菜根提取物的颜色较柔和。上皮细胞质、肌肉、胶原和红细胞都得到了很好的显示。甜菜根提取物的主要成分是甜菜红素；它具有一个离域正电荷和三个羧酸取代基。这些染料是弱酸，其羧酸根阴离子比曙红 Y 更扩散，因此与组织阳离子的结合较弱。龙葵浆果的主要有色成分是前甜菜红素，它除了含有羧酸外，还含有磺酸基团，这有利于酸性染色和更强烈的着色。这两种染料都有氢键形成的潜力，在较小程度上也有一些范德华力形成的潜力。与甜菜根染料一样，与金属如铝形成核染料的络合物不太可能，与龙葵染料也不可能。甜菜红素可用于替代其他红色酸性染料（如曙红）来染色显微镜标本。在测试的两种染料中，龙葵浆果中的前甜菜红素优于红甜菜根中的甜菜红素。这些浆果分布广泛，易于采集；提取过程简单，不需要昂贵的溶剂。
