Spontaneous photosensitization by Heterophyllaea pustulata Hook. f. (Rubiaceae), in sheep from Northwestern Argentina

Primary Photosensitization by Chamaecrista serpens in Santa Inês Sheep

This study aimed to clarify the type of photosensitization induced by C. serpens and to verify if the plant remains toxic after being collected and stored. Eight crossbred sheep, aged between 6 and 36 months, were divided into three groups (G1 to G3). Over 30 days, daily, G1 received an exclusive diet of C. serpens, and G2 and G3 received 10 g/kg/BW and 20 g/kg/BW, respectively. Two other sheep were used as controls (CG). Before administration, the plant had been harvested every 15 days. Liver biopsies and blood samples were taken from all sheep on day zero and weekly. All sheep that received the plant developed clinical signs of photosensitization, and no changes were observed in the serum activities of AST and GGT. On day 30, all sheep except Ov1 from G1 and Ov7 were euthanized and necropsied. All sheep that received the plant developed clinical signs. Macroscopic or histologic lesions were not observed in the liver. Ov 1 recovered 13 days after the end of ingestion. These results demonstrated that C. serpens causes primary photosensitization. It is advisable to avoid grazing on pastures invaded by the plant or to remove them from the pastures immediately after observing the first signs.

Chemistry, Biosynthesis, Physicochemical and Biological Properties of Rubiadin: A Promising Natural Anthraquinone for New Drug Discovery and Development

Anthraquinones (AQs) are found in a variety of consumer products, including foods, nutritional supplements, drugs, and traditional medicines, and have a wide range of pharmacological actions. Rubiadin, a 1,3-dihydroxy-2-methyl anthraquinone, primarily originates from Rubia cordifolia Linn (Rubiaceae). It was first discovered in 1981 and has been reported for many biological activities. However, no review has been reported so far to create awareness about this molecule and its role in future drug discovery. Therefore, the present review aimed to provide comprehensive evidence of Rubiadin's phytochemistry, biosynthesis, physicochemical properties, biological properties and therapeutic potential. Relevant literature was gathered from numerous scientific databases including PubMed, ScienceDirect, Scopus and Google Scholar between 1981 and up-to-date. The distribution of Rubiadin in numerous medicinal plants, as well as its method of isolation, synthesis, characterisation, physiochemical properties and possible biosynthesis pathways, was extensively covered in this review. Following a rigorous screening and tabulating, a thorough description of Rubiadin's biological properties was gathered, which were based on scientific evidences. Rubiadin fits all five of Lipinski's rule for drug-likeness properties. Then, the in depth physiochemical characteristics of Rubiadin were investigated. The simple technique for Rubiadin's isolation from R. cordifolia and the procedure of synthesis was described. Rubiadin is also biosynthesized via the polyketide and chorismate/o-succinylbenzoic acid pathways. Rubiadin is a powerful molecule with anticancer, antiosteoporotic, hepatoprotective, neuroprotective, anti-inflammatory, antidiabetic, antioxidant, antibacterial, antimalarial, antifungal, and antiviral properties. The mechanism of action for the majority of the pharmacological actions reported, however, is unknown. In addition to this review, an in silico molecular docking study was performed against proteins with PDB IDs: 3AOX, 6OLX, 6OSP, and 6SDC to support the anticancer properties of Rubiadin. The toxicity profile, pharmacokinetics and possible structural modifications were also described. Rubiadin was also proven to have the highest binding affinity to the targeted proteins in an in silico study; thus, we believe it may be a potential anticancer molecule. In order to present Rubiadin as a novel candidate for future therapeutic development, advanced studies on preclinical, clinical trials, bioavailability, permeability and administration of safe doses are necessary.

Photosensitization Induced by Heterophyllaea pustulata in Goats: Sequential Development of Skin Lesions

Five adult Saanen goats received a single oral dose of Heterophyllaea pustulata containing 42.25 μg/kg rubiadin (anthraquinone) and 3 adult goats were untreated controls. All goats were exposed to sunlight and sequential ear skin biopsies were collected before treatment and at 32 hours, 3 days, 8 days, and 15 days after treatment. Changes at 32 hours after dosing included epidermal spongiosis, single cell death and acantholysis, an increased BAX/BCL-2 protein ratio, and dermal edema. Lesions at day 3 included epidermal and adnexal necrosis, crust formation, and acanthosis. Acanthosis, hyperkeratosis, and dermal fibrosis and neovascularization were present at day 15. The pro-apoptotic (BAX)/anti-apoptotic (BCL-2) protein ratio increased at 32 hours, whereas epidermal and dermal PCNA immunolabeling increased between days 8 and 15 after treatment. The cutaneous lesions were consistent with sunlight-induced damage, and the occurrence in treated but not control goats indicates photosensitization.

Photosensitisation diseases of animals: Classification and a weight of evidence approach to primary causes

Clare's (1952) classification system for photosensitisation diseases (types I, II, III and Uncertain) has endured many years of use despite some confusion regarding his secondary, or type III, category, as well as the more recent discovery of two mechanisms (types I and II) of phototoxicity. Therefore, to reduce confusion in terminology, I propose that Clare's four groups be known as primary (or direct), secondary (indirect or hepatogenous), endogenous (aberrant porphyrin synthesis), and idiopathic. The use of the word type can then be reserved for the mechanisms of phototoxicity. Clare's (1952, 1955) papers listed three plants as primary photosensitisers and three as idiopathic. In the literature, several other plants have been associated with photosensitisation in farm animals. Most of these are likely to have a primary pathogenesis; however, the weight of evidence for all but a few is sparse. With respect to plants (and certain mycotoxins and insects) implicated in primary photosensitisation outbreaks, McKenzie's "toxicity confidence rankings" (Australia's Poisonous Plants, Fungi and Cyanobacteria, 2012) has been adapted to "phototoxic agent confidence rankings". Thus, plants, mycotoxins or insects can be categorised regarding phototoxicity, i.e. definite (A); some evidence (B); suspected (C); or phototoxin isolated but no field cases known (D), and weight of evidence, i.e. field cases (1); experimental feeding produces photosensitisation (2); phototoxin isolated (3); phototoxin produces photosensitisation experimentally (4); and/or correlation of the action spectrum/chromatogram in blood or skin with the absorption spectrum/chromatogram of the phototoxin (5). As a result, confidence rankings ranging from A5 to D1 can be allocated. From the available literature, at least seventeen plant species can be ranked as A5 (definite phototoxicity with a maximum weight of evidence). The relatively recent breakthrough regarding the discovery of phototoxic anthraquinones in Heterophyllaea spp. has led to the serendipitous association of the same and similar anthraquinones as the most likely phototoxins in alligator weed (Alternanthera philoxeroides).