Correction: Yu, D.Q., et al. Microscopic Characteristic and Chemical Composition Analysis of Three Medicinal Plants and Surface Frosts. Molecules 2019, 24, 4548.

The authors would like to correct an error in the title paper [...].

[Cloning and prokaryotic expression analysis of squalene synthase CpSQS1 and CpSQS2 from Crataegus pinnatifida].

In order to understand the structural characteristics of squalene synthase genes in the triterpenoids biosynthesis pathway of Crataegus pinnatifida, the squalene synthase genes of C. pinnatifida was cloned and analyzed by bioinformatics and prokaryotic expression. Two squalene synthase genes CpSQS1 and CpSQS2 were cloned from C. pinnatifida fruit by RT-PCR. The ORF length of CpSQS1 and CpSQS2 were 1 239 bp and 1 233 bp respectively, encoding 412 aa and 410 aa respectively. CpSQS1 and CpSQS2 were predicted to be stable acidic proteins by online tools. The secondary structure was mainly composed of α-helix structure, and the tertiary structure was predicted by homology modeling. Structural functional domain analysis showed that 35-367 aa of CpSQS1 and CpSQS2 cDNA containing conserved trans-isoprenyl pyrophosphate synthase domains. Transmembrane domain analysis predicted that two transmembrane domains were founded in CpSQS1 and CpSQS2. The squalene synthase amino sequence of C. pinnatifida had higher homology with the known SQS of Salvia miltiorrhiza and Glycyrrhiza glabra. Phylogenetic tree analysis showed that CpSQS1 and CpSQS2 were clustered into one branch of MdSQS1 and MdSQS2, which were consistent with the phylogenetic rule. Prokaryotic expression vector pGEX-4 T-1-CpSQS1 and pGEX-4 T-1-CpSQS2 were transformed into Escherichia coli Transetta(DE3) for induction, and the target protein was successfully expressed at 65 kDa. The expression levels of CpSQS2 were significantly higher than that of CpSQS1 in three different developmental stages of C. pinnatifida. In this study, the full-length cDNA sequences of C. pinnatifida SQS1 and SQS2 were cloned and analyzed for the first time, which provided the foundation for further study on the metabolic pathway of C. pinnatifida triterpenoids.

Microscopic Characteristic and Chemical Composition Analysis of Three Medicinal Plants and Surface Frosts.

The accumulation of chemical constituents of some medicinal plants, such as Paeonia ostii T. Hong et J. X. Zhang, Houpoëa officinalis (Rehder and E. H. Wilson) N. H. Xia and C. Y. Wu. and Atractylodes lancea (Thunb.) DC, can precipitate on the surface and form frosts after natural or artificial intervention. The characteristics of these three medicinal plants and their frosts were analyzed by light microscope, polarizing microscope, stereomicroscope, and metalloscope. The results of ordinary Raman of P. ostii and H. officinalis showed that the frosts of P. ostii matched paeonol, while that of H. officinalis matched magnolol and honokiol. In P. ostii and its frost, 19 peaks were identified by UPLC-Q/TOF-MS, and the main component was paeonol. Eleven components were identified in H. officinalis and its frosts, and the main components were magnolol and honokiol. A. lancea and its frosts were analyzed by gas chromatography-mass spectrometry (GC-MS), 21 were identified, and its main components were hinesol and ß-eudesmol. These three medicinal plants accumulate compounds and precipitate frosts on the surface. The results show that the components of the frosts provide a basis for quality evaluation and research on similar medicinal plants, and reveals the scientific connotation of "taking the medicinal materials' precipitated frosts as the best" of P. ostii, H. officinalis, and A. lancea, to some extent.

[Identification of Corydalis yanhusuo,C. turtschaninovii,C. decumbens by allele-specific PCR].

To establish a DNA molecular markers method for identification of Corydalis yanhusuo,C. turtschaninovii and C. decumbens,the mat K,trn G and psb A-trn H sequences of 56 samples from 14 species of C. yanhusuo,C. turtschaninovii,C. decumbens and their related species were obtained by sequencing. The SNP loci were obtained by Bio Edit 7. 2. 2 software. The primers for AS-PCR identification were designed based on the mutation sites,and the conditions of PCR were optimized to identify C. yanhusuo,C. turtschaninovii,and C. decumbens according to the specific bands. The results showed that the amount of template( 0. 6-1 200 ng)and annealing temperature( 42-60 ℃) had little influence on the amplification results,and the number of cycles had much influence on the amplification results. When the number of cycles was 20,the specific bands of 297 bp( mat K),353 bp( trn G) and 544 bp( mat K) were amplified from C. yanhusuo,C. turtschaninovii and C. decumbens,respectively. The method established in this study had a minimum detection limit of 6 ng for C. yanhusuo,60 ng for C. decumbens and less than 0. 6 ng for C. turtschaninovii. Thus,the allelespecific PCR method established in the research can specifically identify C. yanhusuo,C. turtschaninovii,and C. decumbens.

[Species and medical history of "Xishuang" medicinal materials].

"Xishuang" is a special phenomenon that chemical composition of medicinal materials crystallize on the surface exposed to air for a long time. We summarized Herbal textual research of "Xishuang" phenomenon of six herbs, such as Schisandrae Chinensis Fructus, Moutan Cortex, Atractylodis Rhizoma, Magnoliae Officinalis Cortex, dried persimmon frost and watermelon frost. From historical perspective, cream of Schisandrae Chinensis Fructus was firstly discovered in Lei Gong's Moxibustion Theory. Thereafter, dried persimmon frost was found in Song Dynasty, which was named "white persimmon" in Ben Cao Tu Jing and had become an independent medicine in Compendium of Materia Medica. Then, watermelon frost was found in Yang Yi Da Quan of the Qing Dynasty, and Moutan Cortex's "sand star" was recorded in Zeng Ding Wei Yao Tiao Bian of the Republic of China. After that, "Xishuang" phenomenon of Atractylodis Rhizomaand Magnoliae Officinalis Cortex were reported in 1950s and 1960s in succession. The pattern of "Xishuang" is divided into different type, natural "Xishuang" includes Schisandrae Chinensis Fructus, Moutan Cortex, Atractylodis Rhizoma and Magnoliae Officinalis Cortex, artificial "Xishuang" includes watermelon frost, and dried persimmon frost formed crystals by using artificial intervention. The above 6 kinds of herbs have different crystal structure and chemical composition. Therefore, according to traditional identification experience, "Xishuang" phenomenon is related to varieties and quality of medicinal herbs. These research provide herbalism basis for the modern study of "Xishuang" medicinal materials.