Sunlight exposure is inevitable to all humans and UV radiation in the sunlight usually causes damages to the skin. Tanning, first appearing when UV injures occur, is a pigmentation process which can be considered as a natural defense mechanism of the organism. Melanin plays an important role in the prevention of the skin from harmful environmental factors such as UV radiation. However, the excess accumulation of melanin causes hyperpigmentation, which is associated with a number of unhealthy conditions including solar lentigines, melasma, freckles and post-inflammatory hyperpigmentation. Therefore, the development of safe and effective hypopigmenting agents is of great importance. The depigmenting effects of oxyresveratrol and trans-dihydromorin, as well as moracenin D, sanggenon T, mulberrofuran G and kuwanon O, were investigated in murine b16f10 melanoma cell line and its synergetic non-tumor melanocyte melan-a cells. All these six resorcinol type phenolic compounds (RTPs) were found to reveal significant hypopigmenting effects in murine b16f10 melanoma cell line. Oxyresveratrol and Kuwanon O presented the greatest inhibition on melanin synthesis at low concentration with the suppression on tyrosinase activity. However, in melan-a cells, only oxyresveratrol, trans-dihydromorin, kuwanon O and sanggenon T decreased melanin content significantly. The subsequent mechanisms studies explained the difference. In b16 cells, all of these RTPs induced post-transcriptional degradations of MITF without suppressing its mRNA expression, leading to significant decreases of TRP-1 and TRP-2 production, while in melan-a cells, the levels of tyrosinase, as well as TRP-1and TRP-2 were suppressed by MITF downregulation at both transcription and translation level. Among these RTPs, kuwanon O induced the greatest suppression on the tyrosinase families via MITF down-regulation. Sanggenon T, trans-dihydromorin and oxyresveratrol also exhibited same action of mechanism with weaker activities than kuwanon O. Further evaluations in artificial skin model demonstrated the outstanding depigmenting effects of kuwanon O, sanggenon T and trans-dihydromorin. The inhibitory effect by oxyresveratrol is negligible. It can be therefore inferred that a non-tumor melanocytes system might be more suitable for screening depigmenting agents applied to normal skin cells. Hypopigmenting agents effective in b16 melanoma system may not be so effective on normal melanocytes. Meanwhile, according to the structure-activity relationships studies of theses RTPs, to screen or synthesize resorcinol flavonone derivatives with an isoprenyl group in the Diels-Alder substituent might be a novel approach for the search of potent hypopigmenting agents. The photoprotective effects of these RTPs were also investigated, as UV radiation not only dominants the skin tanning level, but also induces genetic damage and mutations in the epidermal basal layer of human skin. Oxyresveratrol and kuwanon O were found to reveal photoprotective effects on human primary epidermal keratinocytes by enhancement of DNA repair after 4.32 J/cm2 UVA radiation. They exhibited suppressions on cellular ROS induced by UVA and H2O2. Nitrotyrosine levels enhanced by UVA irradiation were also suppressed by them. Moreover, oxyresveratrol even increased cell viability after 4.32 J/cm2 UVA radiation. The possibility of oxyresveratrol and kuwanon O for prevention of photocarcinogenesis in humans is a potential avenue for investigation. In summary, the research contributed to the knowledge of depigmenting and photoprotective effects of resorcinol type phenolic compounds from natural sources. The findings support natural polyphenols as cosmetic ingredients or pharmaceutical composition in purpose of skin lightening or clinic therapy. / published_or_final_version / Biological Sciences / Doctoral / Doctor of Philosophy

Thesis (Ph. D.)--Cornell University, 1909. / "Reprinted from the American chemical journal, vol. XLIV, no. 1, July, 1910."

Thesis (Ph. D.)--Cornell University, 1909. / "Reprinted from the American chemical journal, vol. XLIV, no. 1, July, 1910."

The purpose of this study was to characterise the resinous material formed during the acid catalysed hydrolysis of m-phenylenediamine (MPDA) to resorcinol, and to establish a reaction mechanism that could explain the formation of both resorcinol and the resinous materials in the reaction. A further objective was to determine reaction conditions that would lead to reduced formation of the resins during the hydrolysis reaction. The number of compounds present in a sample taken during the course of the hydrolysis reaction was determined by HPLC fitted with a photodiode array detector. Five main components were detected. These compounds were identified as mphenylenediamine, m-aminophenol, resorcinol, 3,3’-aminodiphenylamine and 3- amino-3’-hydroxydiphenylamine by means of GC-MS. 3,3’-Diaminodiphenylamine is formed by self-condensation of MPDA and 3-amino-3’-hydroxydiphenylamine is formed by the reaction of MPDA with resorcinol. The degree of formation of these intermediates is substantially reduced when MPDA is added dose-wise to phosphoric acid at a reaction temperature of 220oC. The reaction mechanism of the hydrolysis reaction was investigated by isotopic lable incorporation, followed by analysis by NMR. This was done by hydrolysing MPDA using deuterated phosphoric acid (D3PO4). D3PO4 was generated by dissolving phosphorus pentoxide in deuterium oxide. The resorcinol product obtained from the hydrolysis using D3PO4 was found to be deuterated on the C-2, C-4 and C-6 positions. This suggests that the hydrolysis reaction involves protonation of MPDA on these positions, and this results in the formation of an iminium ion as one of the resonance forms. Hydrolysis then occurs on the positively charged carbon of this species. Fertiliser grade phosphoric acid can be used in the hydrolysis reaction, provided sulphates are removed before the acid is used in the hydrolysis reaction. The hydrolysis reaction using either ammonium sulphate or sulphuric acid produces resorcinol in yields lower than 60% if the hydrolysis is conducted in one pass. If these catalysts are used in the hydrolysis reaction, the reaction mixture needs to be re-heated after removal of resorcinol in order to increase the yield. Hydrolysis of MPDA using zirconium phosphate as catalyst gave resorcinol yields in excess of 90% over 24 hours. These reactions were carried out at very low concentrations of MPDA (0.3%). The mode of catalysis in these reactions is unclear. There is a possibility that the reaction is catalysed by phosphoric acid that leaches out of zirconium phosphate at high temperatures. The reaction might therefore not differ mechanistically from the phosphoric acid catalysed reaction. Further studies are required to clarify this point.

An attempt was made to producea -β or Ϫ - resorcinyl alcohol from disubstituted resorcinyls. To accomplish this 3,5-dibromo-β-resorcylic acid was reacted with lithium aluminium hybride, a mild reducing agent, in an attempt to reduce the acid group to the alcohol group. This disubstituted resorcinol was recovered unchanged. 3,5-dibromo-β-resorcyl-aldehyde was reduced by lithium aluminium hydride, but, instead of the alcohol forming, resinification took place. 2-methyl- 4-ethylresorcinol and 4,6-diethyrecorinol were reacted with formaldehyde under alkaline and acidic conditions. In each case a resin formed. The above experlments indicated that condensation took place in the meta position of the resorcinol molecule. Trimethylresorcinol was therefore reacted with formaldehyde under alkaline conditions, resulting in a small quantity ot the alcohol derivative. A better yield of the alcohol derivative was obtained by the hydrolysis or the chloromathyl derivative. In pursuing this line, a seres of new compounds and their derivatives were prepared. The condensation of the alcohol derivative with trimethylresorcinol and also with resorcinol was investigated.

No description available.

No description available.

No description available.

Thesis (Ph. D.)--University of Illinois, 1922. / Vita. Caption title: Rings through the meta and para positions of benzene. A study of certain ethers of resorcinol and meta-aminophenol, by W.C. Wilson with Roger Adams. "Reprinted from the Journal of the American chemical society, vol. XLV, no. 2. February, 1923."

The ultimate objective of this research is the elucidation of the mechanism of the resorcinol-formaldehyde condensation. Whilst a vast literature has been built up about the phenol- formaldehyde condensation, that of resorcinol has received but scant attention, probably because the high reactivity of resorcinol rendered the following of the condensation extremely difficult. The earliest observation concerning the resorcinol-formaldehyde condensation was due to Baeyer who, in 1872, condensed resorcinol with various aldehydes. When the aldehyde was relatively inactive crystalline compounds were obtalned but with acetaldehyde or formaldehyde a resinous product resulted. In 1892 Caro condensed an excess ot resorcinol with formaldehyde in the presence of dilute hydrochloric acid; the product obtained recrystallised from alcohol as white microsoopic crystals, decomposed without melting at 250° and was stated to be bis (2- 4 dihydroxyphenyl) methane ... In decidlng upon the most suitable lines of attack it would seem that a survey of the literature relating to the phenol-formaldehyde concentration which might be expected to be closely related to that of resorcinol, would be of value. Summary of p. 1-5