Oxalic acid in ginger specifically denatures the acrid raphides in the unprocessed dried tuber of Pinellia ternata

Objective:Pinellia Tuber,the dried tuber of Pinellia ternata,is widely used in Japanese Kampo medicines and traditional Chinese medicines.The unprocessed Pinellia Tuber is known to cause very strong acrid irritation at oral and laryngopharynx mucosa.Recent studies have shown that the sharp needle-like crystals called raphides,that are composed of calcium oxalate and proteins,are the main causative substances of the irritation.Ginger,the rhizome of Zingiber officinale,has been used in the processing to reduce the acridity of Pinellia Tuber since before the sixth century,however,the mechanisms of reducing acridity have not been scientifically proved yet.Methods:We developed the raphides denaturation assay(RDA)to quantify the degree of denaturation in the raphides to cause irritation.By their lipophilic characters,the raphides could be extracted in petroleum ether(PE)layer from powdered Pinellia Tuber suspended in water,and the contents of the raphides in PE layer were measured by the absorbance.By this assay,we conducted the activity-guided fractionation from the boiling water extract of ginger to find the ingredients to denature the raphides.We also conducted the gustatory tests to detect the change of the irritation of the denatured raphides.Results:The treatment of powdered Pinellia Tuber suspension with ginger extract reduced the distribution of raphides in PE layer in RDA in a concentration-dependent manner.The activity-guided fractionation using RDA revealed that oxalic acid was the main active ingredient in ginger extract to denature the raphides of Pinellia Tuber.Oxalic acid reduced the lipophilicity of the raphides in the thermo-,time-,and concentration-dependent manners,and its activity was affected by pH.The treatment of powdered Pinellia Tuber suspension with oxalic acid significantly reduced its acrid irritation in gustatory test in human.Conclusions:We found that oxalic acid is the main active ingredient in ginger to reduce the acrid irritation of Pinellia Tuber.

Biogenic carbonate formation and sedimentation in the Xisha Islands: evidences from living Halimeda

A recent island survey reveals that the Xuande Atoll and the Yongle Atoll in the Xisha Islands can be classified into one of two systems：the depleted atoll system and growth atoll system;the survey also indicates that the decreased area of several shoals is an unbearable burden for the Xisha Islands, of which the largest island area is 2.13 km2 and the minimum elevation is 1.4 m. According to a survey on the ecological characteristics of Halimeda in the Laolongtou breaker zone of Shidao Island in the Xisha Islands, the green and white living Halimeda are collected, the isotopic ages of 14C contained in the Halimeda are shown to be 27 years and 55 years, respectively, and carbonate mainly occurs in five types, i.e., luster, segment, sand, sand grain, and marl in the formation. The Halimeda segments mainly provide the carbonate sediments of long-term biogenic deposits in the reef environment and the annual productivity per area is 60–100 g/m2;the characteristics of the microstructure of the Halimeda are analyzed, the aragonite raphide carbonate is deposited and enriched in the cortexes, medullas and cysts, and the Halimeda generally contain major elements such as C, O, Ca, Cl, Mg, K, Na, S and Al, and are rich in trace elements such as tellurium （Te）, rhodium （Rh） and strontium. It is believed that the Halimeda grow slowly, including the biotic community of reef corals in the reef areas, thus they possess an environmental remediation capacity, but it takes much time to remedy the environment, and it is necessary to make the law to protect the diversity and vulnerability of the Xisha marine ecology, the ecology of the reef community and the island environment in a scientific way. As indicated in the survey, under the background of global warming and sea-level rise, the discovery of large amounts of Halimeda in the Laolongtou sea area is significant for the natural increase of the depleted atoll system of the Xuande Atoll, while the Halimeda segments represent the primary form of the fossil Halimeda, of which the species can be identified and preserved in great numbers under geological conditions. The Miocene was discovered in large amounts in the Xichen-1 well, therefore the study on the characteristics and mechanism of Halimeda carbonate sediments plays a pivotal role in the formation and construction of organic reefs in the South China Sea as well as oil and gas exploration.