Plant toxins: alkaloids and their toxicities

Since ancient civilization, plants have been utilized in many aspects of life, especially in medicinal purposes due to the presence of distinctive secondary metabolites like alkaloids, phenolics and terpenoids. Among them, alkaloids represent a large group of secondary metabolites that have basic properties and comprise nitrogen atom within the heterocyclic ring. Plant synthesizes alkaloids to maintain their survivability under unfavorable conditions. Over 3000 years, indigenous people have been used alkaloid-containing plant extracts to treat several ailments such as fever, snakebite and insanity. However, despite significant benefits to humans and pharmaceutical industries, some of the plant alkaloids are categorized as main plant toxins due to their enormous structural diversity and various modes of actions. Humans and animals can be exposed to toxic alkaloids either through inhalation, swallowing or by direct contact, therefore leads to the specific mechanism that involves receptors, transporters, enzymes and genetic materials at specific cells and tissues, hence may cause hepatotoxic effects and musculoskeletal deformities. This review focuses on some of the plant alkaloids such as pyrrolizidine, tropane, piperidine and indolizidine, which can give various side effects on humans and animals such as itching, nausea, vomiting, mild gastrointestinal perturbation, psychosis, paralysis, teratogenicity, arrhythmias and sudden death

Induction, multiplication, and evaluation of antioxidant activity of Polyalthia bullata callus, a woody medicinal plant

Polyalthia bullata is an endangered medicinal plant species. Hence, establishment of P. bullata callus culture is hoped to assist in mass production of secondary metabolites. Leaf and midrib were explants for callus induction. Both of them were cultured on Murashige and Skoog (MS) and Woody Plant Medium (WPM) containing different types and concentrations of auxins (2,4-dichlorophenoxyacetic acid (2,4-D), α-naphthaleneacetic acid (NAA), picloram, and dicamba). The callus produced was further multiplied on MS and WPM supplemented with different concentrations of 2,4-D, NAA, picloram, dicamba, indole-3-acetic acid (IAA), and indole-3-butyric acid (IBA) media. The quantification of total phenolic content (TPC), total flavonoid content (TFC) and antioxidant capacity was further carried out on P. bullata callus, and the results were subjected to correlation analysis. Among the media, the WPM + 16.56 µM picloram (53.33 ± 22.06%) was the best for callus induction while MS + 30 µM dicamba was the best for callus multiplication. The TPC, TFC, and EC50 of DPPH scavenging activity were determined at 0.657 ± 0.07 mg GAE/g FW, 0.491 ± 0.03 mg QE/g, and 85.59 ± 6.09 µg/mL in P. bullata callus, respectively. The positive correlation between DPPH scavenging activity with TPC was determined at r = 0.869, and that of TFC was at r = 0.904. Hence, the P. bullata callus has an ability to accumulate antioxidants. It therefore can be a medium for secondary metabolites production

Phytochemical content in Polyalthia bullata king and the effect of auxins, elicitors and precursors on total alkaloid content in callus

Polyalthia bullata or locally known as Tongkat Ali Hitam is one of the species belongs to genus of Polyalthia. The plant has been reported to possess an ability to treat many diseases and enhance human health and life quality, which might be contributed by the presence of bioactive compounds. However, due to limited reports on phytochemical compounds present in P. bullata, the phytochemical profiling can help in clarifying the types of phytocompounds, therefore, choosing the right extraction solvent is important in order to get optimum yield. One of the factors that might affect the extraction yield is the polarity of extraction solvent. Apart from that, overcollection of P. bullata from wild habitat has become serious problem that may lead to species extinction. The establishment of P. bullata callus culture and addition of elicitors and precursors can help in enhancing the production of phytochemical compounds, therefore reducing the extinction of P. bullata from native habitat. Hence, the aims of this study were to determine the total alkaloid content (TAC), total phenolic content (TPC), total flavonoid content (TFC), and total terpenoid content (TTC) as well as antioxidant activity of hexanic, ethanolic, methanolic, and distilled water extracts of P. bullata root, leaf and stem, to profile biochemical compounds using gas chromatography- mass spectrometry (GC-MS), to induce callus from P. bullata using different explants, basal media, and plant growth regulators (PGRs), and to determine the effectiveness of auxins, precursors, and elicitors in enhancing alkaloid production in callus. For callus induction, the sterilized leaf and midrib explants were used and cultured on Murashige and Skoog (MS) and Woody Plant Medium (WPM) basal media supplemented with B5 vitamin, and different concentrations and types of auxins (2,4-dichlorophenoxyacetic acid (2,4-D), α- naphthaleneacetic acid (NAA), picloram and dicamba). The MS and WPM basal media supplemented with different types and concentrations (10, 20, 30, 40 50 μM) of auxins (2,4-D, NAA, picloram, dicamba, indole-3-acetic acid (IAA), indole-3-butyric acid (IBA)) were used to determine the best multiplication medium and alkaloid content after six weeks of culture. The elicitors (methyl jasmonate (MeJA), salicylic acid (SA), and chitosan) and precursors (L-phenylalanine, L-tyrosine, and L-tryptophan) at concentration of 50, 100 and 150 μM was respectively added into the best alkaloid production medium to enhance the alkaloid production. The results from the studies revealed that the methanolic extract of P. bullata leaf exhibited the highest TPC, TFC, TTC and total antioxidant activity at 1042.52 ± 1.97 mg GAE/g DW, 80.88 ± 0.24 mg QE/g DW, 0.19 ± 0.00 mg LE/g DW and 85.19 ± 1.16%, respectively. Meanwhile, the methanolic extract of P. bullata stem showed the highest TAC at 7.71 ± 0.00 mg AE/g DW. The fatty acids, phenolics, and carboxylic acid were found in methanolic stem extract; carbohydrates, alkaloids, and fatty acids were found in methanolic root extract; and terpenoids, phenolics, and alcohol were found in methanolic leaf extract of P. bullata using GC-MS. Among the media tested for in vitro callus induction, WPM basal medium supplemented with 16.56 μM picloram exhibited the highest callus induction percentage with 53.33 ± 22.06%. As for the callus multiplication, the callus cultured on MS + 30 μM dicamba was found to significantly produce the highest fresh weight (1180.00 ± 159.43 mg FW) and dry weight (58.00 ± 6.66 mg DW) of callus after three weeks of culture. The addition of auxins into culture medium managed to enhance the alkaloid production in callus with the highest alkaloid content was observed in callus cultured on MS medium supplemented with 30 μM 2,4-D (31.07 ± 0.05 μg/g DW). Among auxins, elicitors, and precursors tested, the MS + 30 μM 2,4-D and MS + 30 μM 2,4-D + 50 μM chitosan were found to be the best media for alkaloid production with the amount of 31.07 ± 0.05 and 31.30 ± 0.23 μg/mg DW after six weeks of culture, respectively. As a conclusion, methanol was found to be the best extraction solvent to extract phytochemical compounds from P. bullata. The incorporation of auxins like 2,4-D into the culture medium is the best strategy to enhance alkaloid production in P. bullata callus. Therefore, the data obtained from this study can be used to further investigate biological activities of phytochemical compounds present in P. bullata, and therefore can reduce overcollection of this plant from the forest