A Draft Genome of the Ginger Species Alpinia nigra and New Insights into the Genetic Basis of Flexistyly

Angiosperms possess various strategies to ensure reproductive success, such as stylar polymorphisms that encourage outcrossing. Here, we investigate the genetic basis of one such dimorphism that combines both temporal and spatial separation of sexual function, termed flexistyly. It is a floral strategy characterised by the presence of two morphs that differ in the timing of stylar movement. We performed a de novo assembly of the genome of Alpinia nigra using high-depth genomic sequencing. We then used Pool-seq to identify candidate regions for flexistyly based on allele frequency or coverage differences between pools of anaflexistylous and cataflexistylous morphs. The final genome assembly size was 2 Gb, and showed no evidence of recent polyploidy. The Pool-seq did not reveal large regions with high FST values, suggesting large structural chromosomal polymorphisms are unlikely to underlie differences between morphs. Similarly, no region had a 1:2 mapping depth ratio which would be indicative of hemizygosity. We propose that flexistyly is governed by a small genomic region that might be difficult to detect with Pool-seq, or a complex genomic region that proved difficult to assemble. Our genome will be a valuable resource for future studies of gingers, and provides the first steps towards characterising this complex floral phenotype.

Physicochemical Properties and Bioactivities of Six Alpinia Species in Sri Lanka

Plants comprising bioactive substances with therapeutic value have progressively become the object of research studies. Many species of the genus Alpinia provide a variety of medicinal properties. This study was undertaken to study the biological activities and physicochemical properties of rhizomes and leaves of six Alpinia species available in Sri Lanka namely, Alpinia malaccensis, Alpinia calcarata, Alpinia galanga, Alpinia nigra, Alpinia calcarata Wild and Alpinia purpurata. Physicochemical parameters will be helpful in standardization for quality, purity and authentication of these medicinal plants. Methanol extracts from rhizomes and leaves were screened for total polyphenol content (TPC), antioxidant activity and α-amylase inhibition activities. Extracted powders were analysed for physicochemical constants such as loss on drying, total ash, acid -insoluble ash and water-soluble ash contents. The TPC of dried leaves of Alpinia calcarata Wild was the highest of all tested as 2.186±0.027 g of GA equivalents per 1 g of dried rhizome. The Methanol extracts of the rhizome and leaf samples of six species showed reasonable antioxidant activity in the DPPH radical scavenging assay. Interestingly the rhizome extracts of Alpinia nigra and Alpinia purpurata exhibited higher α-amylase inhibitory activities (29.417±0.507 and 29.676 ± 0.107 µg/mL respectively) compared with the Acarbose, which is an anti-diabetic drug (28.273 ± 0.615 µg/mL). The results revealed that the Sri Lankan Alpinia species have a potency to be used as a source of antioxidant and anti-diabetic agents and it is important to increase the value of the unexplored medicinal herbs available in Sri Lanka.

Antioxidant, Antityrosinase Activity and Toxicity of Alpinia nigra Extracts

Excessive of ultraviolet light causes abnormality of melanin production. Antioxidants and antityrosinase agents are able to reduce hyperpigmentation by interrupting the process of melanin production. The purpose of this study is to examine the antioxidant and antityrosinase activities as well as toxicity of both 80% ethanol and aqueous extracts of Alpinia nigra by DPPH free radical scavenging assay, mushroom tyrosinase assay and brine shrimp lethality bioassay. Alpinia nigra extracts showed positive result on antioxidant and antityrosinase activities. We found that extract of A. nigra’s leaf has the most effective activity of antioxidant and antityrosinase among other parts of this plant. The ethanol and aqueous extracts from the leaf of A. nigra at the concentration of 125 μg/mL showed % inhibition for free radical scavenging as 94.97% and 93.35%, respectively. The IC50 values of antioxidant were 39.83±16.21 and 46.33±15.22 μg/mL, respectively. In addition, ethanol extract of the leaf from A. nigra at the concentration of 1,000 μg/mL produced 92.61% inhibition of mushroom tyrosinase activity, whereas aqueous extract of A. nigra’s leaf at the same concentration produced 74.47% inhibition. The IC50 of antityrosinase activities were 142.81±13.32 and 406.88±66.43 μg/mL for ethanol and aqueous extracts, respectively. Moreover, the brine shrimp lethality bioassay showed that all extracts were non-toxic (LC50 >1,000 μg/mL). In conclusion, the ethanol extract of A. nigra’s leaf may be beneficial and provide the novel and safe source for antioxidant and whitening agent.