PPD Derivatives Research Articles

Synthesis and antibacterial activities of heterocyclic ring-fused 20(S)-protopanaxadiol derivatives

Multidrug-resistant (MDR) bacterial infections are becoming a life-threatening issue in public health; therefore, it is urgent to develop novel antibacterial agents for treating infections caused by MDR bacteria. The 20(S)-protopanaxadiol (PPD) derivative 9 was identified as a novel antibacterial hit compound in screening of our small synthetic natural product-like (NPL) library. A series of novel PPD derivatives with heterocyclic rings fused at the C-2 and C-3 positions of the A-ring were synthesized and their antibacterial activities against Staphylococcus aureus (S. aureus) Newman strain and MDR S. aureus strains (USA300, NRS-1, NRS-70, NRS-100, NRS-108, NRS-271, XJ017, and XJ036) were evaluated. Among these compounds, quinoxaline derivative 56 (SH617) exhibited the highest activity with MICs of 0.5–4 μg/mL against the S. aureus Newman strain and the eight MDR S. aureus strains. Its antibacterial activity was comparable to that of the positive control, vancomycin. In the zebrafish, 56 revealed no obvious toxicity even at a high administered dose. In vivo, following a lethal infection induced by USA300 strains in zebrafish, 56 exhibited significantly increased survival rates in a dose-dependent manner.

Synthesis and Biological Evaluation of Heterocyclic Ring-Fused 20(S)-Protopanaxadiol Derivatives as Potent Antiosteoporosis Agents.

A series of heterocyclic ring-fused derivatives of 20(S)-protopanaxadiol (PPD) were synthesized and evaluated for their inhibitory effects on RANKL-induced osteoclastogenesis. Among these compounds, 33 (SH491, IC50 = 11.8 nM) showed the highest potency with 100% inhibition at 0.1 μM and 44.4% inhibition at an even lower concentration of 0.01 μM, which was much more potent than the lead compound PPD (IC50 = 10.3 μM). Cytotoxicity tests indicated that the inhibitory effect of these compounds on RANKL-induced osteoclast differentiation was not due to their cytotoxicity. Interestingly, SH491 also exhibited a notable impact on the osteoblastogenesis of MC3T3-E1 preosteoblasts. Mechanistic studies revealed that SH491 inhibits the expression of osteoclastogenesis-related marker genes and proteins, including TRAP, CTSK, MMP-9, and ATPase v0d2. In vivo, SH491 could dramatically decrease the ovariectomy-induced osteoclast activity and relieve osteoporosis obviously. Thus, these PPD derivatives could be served as promising leads for the development of novel antiosteoporosis agents.

Investigations on detoxification mechanisms of novel para-phenylenediamine analogues through N-acetyltransferase 1 (NAT-1).

Para-phenylenediamine (PPD) is one of the most used chemicals in oxidative hair dyes. However, its use has been associated with adverse effects on health, including contact dermatitis and other systemic toxicities. Novel PPD derivatives have been proposed as a safer replacement for PPD. This can be achieved if these molecules minimally permeate the skin and/or are easily metabolised by enzymes in the skin (e.g., N-acetyltransferase-1 (NAT-1)) into innocuous compounds before gaining systemic entry. This study investigated the detoxification pathway mediated by NAT-1 enzymes on 6 synthesized PPD analogues (namely, P1-P6) with different chemical properties, to study the role of functional groups on detoxification mechanisms in HaCaT skin cells. These compounds were carefully designed with different chemical properties (whereby the ortho position of PPD was substituted by nucleophile and electrophile groups to promote N-acetylation reactions, metabolism and clearance). Compounds P2-P4 N-acetylated at 54-49nmol/mg/min, which is 1.6 times higher than N-acetylation of PPD, upregulated NAT-1 activity from 8-7% at 50μM to 22-11% at 100μM and showed 4 times higher rate of elimination (k equal to 0.141 ± 0.016-0.124 ± 0.01h-1) and 3 times faster rate of clearance (0.172 ± 0.007-0.158 ± 0.005h-1mgprotein-1) than PPD (0.0316 ± 0.0019h-1, 0.0576 ± 0.003h-1mg protein-1, respectively). The data suggest that nucleophile substituted compounds detoxify at a faster rate than PPD. Our metabolic and detoxification mechanistic studies revealed significantly higher rates of N-acetylation, NAT-1 activity and higher detoxification of P2-P4 in keratinocytes, suggesting the importance of nucleophilic groups at the ortho position in PPD to reduce toxicity of aniline-based dyes on human skin cells.

Effects of replacing benzodithiophene with a benzothiadiazole derivative on an efficient wide band-gap benzodithiophene-alt-pyrrolo[3,4-c]pyrrole-1,3(2H,5H)-dione copolymer

In this study, we investigated the property modulation of a high energy converting, wide-band-gap, alternating polymer, P(BDTT-PPD), comprising benzodithiophene (BDTT) and pyrrolo[3,4-c]pyrrole-1,3(2H,5H)-dione (PPD) derivatives by replacing BDTT with 4,7-di(thiophen-2-yl)benzo[c][1,2,5]thiadiazole (DTBT). The new alternating polymer, named P(DTBT-PPD), was prepared by polymerizing distannyl DTBT and dibromo PPD derivatives, with the aim of making a PPD-based, low-band-gap polymer for solar cell applications. Polymer P(DTBT-PPD) displayed an intense absorption band between 300 and 750 nm with two distinct absorption maxima at 439 and 605 nm as a film. The calculated optical band-gap (Eg) was 1.64 eV. The determined highest occupied and lowest unoccupied molecular (HOMO and LUMO, respectively) orbital energy levels of P(DTBT-PPD) were −5.30 and −3.66 eV, respectively. Solution-processed organic solar cells (OSCs), made with P(DTBT-PPD):PC70BM ([6,6]-Phenyl C71 butyric acid methyl ester), provided a maximum power-conversion efficiency (PCE) of 2.23%. P(DTBT-PPD) displayed much lower Eg (≈0.4 eV), slightly higher HOMO level (≈0.14 eV), and considerably lower PCE (≈4%), than P(BDTT-PPD). The increased curvature of P(DTBT-PPD) chains could be the main reason for their lower PCE than P(BDTT-PPD).

One-pot synthesis, anti-tumor evaluation and structure-activity relationships of novel 25-OCH3-PPD derivatives.

Based on the fact that 25-OCH3-PPD, a natural ginsengenin isolated from the leaves of Panax ginseng, is a promising lead compound, novel 25-OCH3-PPD derivatives were synthesized to find more potent anti-tumor agents by a simple and facile synthetic method. These derivatives were classified into three types and screened for their cytotoxic activities against seven human cancer cell lines. Compared with 25-OCH3-PPD, compounds a5, a7, b5 and b7 exhibited higher anti-tumor activities on all tested cell lines with almost 5-fold to 15-fold increases. In particular, compound a7 showed the greatest cytotoxic activity against α-2 cells (IC50 = 2.4 ± 0.4 μM). The preliminary study on the mechanisms indicated that compound a7 could induce α-2 cell apoptosis. Structure-activity relationships demonstrated that the carbon-carbon double bond at the C-20 position could enhance the antiproliferative activity. In conclusion, the novel derivatives a5, a7, b5 and b7 could be further studied as potential candidates for the treatment of cancer. This research provides a theoretical reference for the exploration of new antiproliferative agents.

A 20(S)-protopanoxadiol derivative overcomes multi-drug resistance by antagonizing ATP-binding cassette subfamily B member 1 transporter function.

In cancer cells, failure of chemotherapy is often caused by the ATP-binding cassette subfamily B member 1 (ABCB1), and few drugs have been successfully developed to overcome ABCB1-mediated multi-drug resistance (MDR). To suppress ABCB1 activity, we previously designed and synthesized a new series of derivatives based on 20(S)-protopanoxadiol (PPD). In the present study, we investigated the role of PPD derivatives in the function of ABC transporters. Non-toxic concentrations of the PPD derivative PPD12 sensitized ABCB1-overexpressing cells to their anti-cancer substrates better than either the parental PPD or inactive PPD11. PPD12 increased intracellular accumulation of adriamycin and rhodamine123 in resistant cancer cells. Although PPD12 did not suppress the expression of ABCB1 mRNA or protein, it stimulated the activity of ABCB1 ATPase. Because PPD12 is a competitive inhibitor, it was predicted to bind to the large hydrophobic cavity of homology-modeled human ABCB1. PPD12 also enhanced the efficacy of adriamycin against ABCB1-overexpressing KB/VCR xenografts in nude mice. In conclusion, PPD12 enhances the efficacy of substrate drugs in ABCB1-overexpressing cancer cells. These findings suggest that a combination therapy consisting of PPD12 with conventional chemotherapeutic agents may be an effective treatment for ABCB1-mediated MDR cancer patients.

Real‐time detection of p‐phenylenediamine penetration into human skin by in vivoRaman spectroscopy

Penetration, autoxidation and N-acetylation of p-phenylenediamine (PPD) have been studied in vitro and ex vivo. However, a clear understanding of in vivo PPD penetration and the formation of PPD derivatives is lacking. To obtain insights into the in vivo penetration, clearance and formation of PPD derivatives in human skin. Patch test chambers containing PPD 1% pet. were applied to the forearms of two human volunteers, with increasing application times. Non-invasive Raman microspectroscopy was used for detection of PPD (derivatives) in skin at several follow-up times. Application of a PPD 1% pet. patch for 30 min resulted in substantial amounts of PPD in the stratum corneum of 90 mg PPD/g keratin. PPD contents were highest after three applications for 1 h each (330 mg PPD/g keratin), followed by single applications for 2 h 40 min, 2 h, and 23 h. The PPD half-time in the skin was 3 h. No spectral contributions of Bandrowski's base, monoacetyl-PPD and diacetyl-PPD were detected. We have gained insights into the in vivo penetration of PPD in human skin by using non-invasive Raman spectroscopy. Penetration into the skin was fast, and the PPD concentrations detected in the stratum corneum were high. PPD was detected in both the stratum corneum and the viable epidermis. Oxidized or acetylated PPD derivatives could not be detected.

The clinical spectrum of reactions developed based on paraphenylenediamine hypersensitivity two pediatric cases.

The clinical spectrum of reactions developed based on paraphenylenediamine hypersensitivity two pediatric cases.

Discovery, synthesis, and structure–activity relationships of 20(S)-protopanaxadiol (PPD) derivatives as a novel class of AMPKα2β1γ1 activators

Adenosine 5′-monophosphate-activated protein kinase (AMPK) has been demonstrated as a promising drug target due to its regulatory function in glucose and lipid metabolism. 20(S)-protopanoxadiol (PPD) was firstly identified from high throughput screening as a small molecule activator of AMPK subtype α2β1γ1. In order to enhance its potency on AMPK, a series of PPD derivatives were synthesized and evaluated. Structure–activity relationship study showed that the amine derivatives at the 24-position (groups I–VI) can improve the potency (EC50: 0.7–2.3 μM) and efficacy (fold: 2.5–3.8). Among them, compounds 12 and 13 exhibited the best potency (EC50: 1.2 and 0.7 μM) and efficacy (fold: 3.7 and 3.8). Further study suggested the mechanism of AMPK activation may functioned at the allosteric position, resulting the inhibition of the lipid synthesis in HepG2 cell model.

20(S)-Protopanaxadiol (PPD) analogues chemosensitize multidrug-resistant cancer cells to clinical anticancer drugs

Novel 20(S)-protopanoxadiol (PPD) analogues were designed, synthesized, and evaluated for the chemosensitizing activity against a multidrug resistant (MDR) cell line (KBvcr) overexpressing P-glycoprotein (P-gp). Structure–activity relationship analysis showed that aromatic substituted aliphatic amine at the 24-positions (groups V) effectively and significantly sensitized P-gp overexpressing multidrug resistant (MDR) cells to anticancer drugs, such as docetaxel (DOC), vincristine (VCR), and adriamycin (ADM). PPD derivatives 12 and 18 showed 1.3–2.6 times more effective reversal ability than verapamil (VER) for DOC and VCR. Importantly, no cytotoxicity was observed by the active PPD analogues (5μM) against both non-MDR and MDR cells, suggesting that PPD analogues serve as novel lead compounds toward a potent and safe resistance modulator. Moreover, a preliminary mechanism study demonstrated that the chemosensitizing activity of PPD analogues results from inhibition of P-glycoprotein (P-gp) overexpressed in MDR cancer cells.

Penetration and haptenation of p‐phenylenediamine

Although p-phenylenediamine (PPD) has been recognized as an extreme sensitizer for many years, the exact mechanism of sensitization has not been elucidated yet. Penetration and the ability to bind to proteins are the first two hurdles that an allergen has to overcome to be able to sensitize. This review is an overview of studies regarding PPD penetration through skin (analogues) and studies on the amino acids that are targeted by PPD. To complete this review, the auto-oxidation and N-acetylation steps involved in PPD metabolism are described. In summary, under normal hair dyeing exposure conditions, <1% of the applied PPD dose penetrates the skin. The majority (>80%) of PPD that penetrates will be converted into the detoxification products monoacetyl-PPD and diacetyl-PPD by the N-acetyltransferase enzymes. The small amount of PPD that does not become N-acetylated is susceptible to auto-oxidation reactions, yielding protein-reactive PPD derivatives. These derivatives may bind to specific amino acids, and some of the formed adducts might be the complexes responsible for sensitization. However, true in vivo evidence is lacking, and further research to unravel the definite mechanism of sensitization is needed.

Synthesis of protopanaxadiol derivatives and evaluation of their anticancer activities

Protopanaxadiol (PPD), an aglycon of ginseng saponins, has shown anticancer activity in earlier studies. Here, we have reported the semisynthesis of nine PPD derivatives with acetyl substitutions. Subsequently, the antiproliferative effects of these nine analogs on different human cancer cell lines have been investigated. Compounds 1, 3, and 5 showed more significant and more potent antiproliferative activity compared with PPD and other derivatives. A flow cytometric assay indicated that compounds 1, 3, and 5 arrested cell cycle progression in the G1 phase and significantly induced apoptosis of cancer cells.

Effect of protopanaxadiol derivatives in high glucose-induced fibronectin expression in primary cultured rat mesangial cells: Role of mitogen-activated protein kinases and Akt

A lot of anti-diabetic agents using natural plants have been extensively studied. Ginsenosides are known to be used as a remedy for diabetes in Asian countries and American Societies. Diabetic nephropathy is a major complication of diabetes mellitus. Extracellular matrix in mesangial cells is mainly composed of fibronectin and the increase of fibronectin is a hallmark of diabetic nephropathy. Protopenaxadiol (PPD) is a major component of total ginseng. Thus, we examined the regulatory mechanism of PPD derivatives-induced preventive effect of fibronectin expression in mesangial cells cultivated under diabetic condition. In present study, ginsenoside Rb1 prevented the high glucose-induced increase of fibronectin expression in mesangial cells. Ginsenoside Rb2 and Rg3 also mildly inhibited it. However, ginsenoside Rc and Rd did not prevent the high glucose-induced increase of fibronectin expression in mesangial cells. In addition, ginsenoside Rb1 prevented high glucose-induced phosphorylation of p44/42 mitogen activated protein kinase (MAPK), p38 MAPK, JNK/SAPK, and Akt. These results suggest that ginsenoside Rb1 is the most powerful component of PPD derivatives. In conclusion, ginsenoside Rb1 prevented high glucose-induced increase of fibronectin expression via the inhibition of MAPK-Akt signaling cascade.

Skin sensitization potency and cross‐reactivity of p‐phenylenediamine and its derivatives evaluated by non‐radioactive murine local lymph node assay and guinea‐pig maximization test

p-Phenylenediamine (PPD)-related chemicals have been used as antioxidants in rubber products, and many cases of contact dermatitis caused by these chemicals have been reported. The aim of this study was to investigate relative sensitizing potency and cross-reactivity among PPD derivatives. Five PPD derivatives, p-aminodiphenylamine (PADPA), N,N'-diphenyl-p-phenylenediamine (DPPD), N-isopropyl-N'-phenyl-p-phenylenediamine (IPPD), N-(1,3-dimethylbutyl)-N'-phenyl-p-phenylenediamine (DMBPPD), N-(1-methylheptyl)-N'-phenyl-p-phenylenediamine (MHPPD), and the core chemical PPD were evaluated for their sensitizing potency and cross-reactivity using the non-radioactive murine local lymph node assay (LLNA) and the guinea-pig maximization test (GPMT). PPD and all the derivatives were identified as primary sensitizers in both tests. The order of potency in the LLNA was as follows: IPPD and PADPA > PPD > DMBPPD and MHPPD > DPPD. In the GPMT, all six groups of animals sensitized with one of these chemicals cross-reacted to four other derivatives. Specifically, the five groups that have a common basic PADPA structure, that is PADPA, DPPD, IPPD, DMBPPD, and MHPPD, all reacted to each other at almost the same scores, while none of them reacted to PPD. The cross-reactivity profile found in the study was to some extent different from that in previous human data, where distinction between cross-reaction and concomitant primary sensitization is not always clear.

Elicitation response characteristics to mono‐ and to N,N′‐diacetyl‐para‐phenylenediamine

Para-phenylenediamine (PPD) is an important and common cause of allergic contact dermatitis. The mechanism of sensitization is still unknown. It is believed that PPD is a prohapten and thus the balance between activation and/or detoxification processes may influence responses to PPD. Beside auto-oxidation to Bandrowski's base, PPD is enzymatically acetylated to monoacetyl-PPD (MAPPD) and to N,N'-diacetyl-PPD (DAPPD) in skin and keratinocytes. We investigated if the 2 acetylated PPD derivatives are able to elicit allergic contact dermatitis by performing epicutaneous skin tests in subjects with dermatitis. Contact allergy to PPD and the 2 acetylated derivatives (1% in petrolatum) were detected by patch testing of 455 patients with eczema from our clinic who were tested with the baseline series. 16 subjects were found to be patch test positive to PPD (3.5%). No reactions were found for MAPPD, and just 1 PPD-positive patient was positive for DAPPD (0.2%). In agreement with our earlier published in vitro data, these in vivo patch test results indicate that acetylation of PPD can be regarded as a detoxification reaction.

Investigations on Initial Stage of Aging of Tire Rubbers by Chemiluminescence Spectroscopy

Abstract The initial stage of the thermal oxidation aging process of polydienes (NR, BR, and SBRs) and polyolefins (EPDM) was investigated using the chemiluminescence (CL) method, which detects the low-intensity light emitted by the polymer oxidation reaction as a function of time. It thus quantitatively characterizes the kinetics of the polymer oxidation reaction and the aspect of the polymer microstructure during the thermal oxidation condition, the influence of the rubber mixture's ingredients or vulcanizates, and the role of the anti-aging agent. The oxidation induction time (OIT) — defined as the time at which the oxidation reaction starts — is introduced as the analytical result of CL analysis, with a standard deviation of 5–6%. The OIT from CL analysis indicates the resistance of the polymer against the thermal oxidation condition. The polydiene microstructure is found to play a significant role in the aging behavior of polymers. In the case of polydienes with higher double-bond concentration in the main chain (1,4 units) — NR or BR, for example — the OIT occurs after a relatively brief exposure to thermal influences and oxygen, depending on the temperature. SBR, with a high vinyl (1,2-butadiene units) or styrene content, is relatively more resistant than NR or BR to radical attack by oxidation reaction. EPDM with no double bonds in the main polymer chain exhibits, moreover, the strongest aging resistance. After extraction of the polymers to remove the stabilizer commonly added to the polymer, OIT values are as much as 400% shorter than for raw polymers. The OIT values of polymers processed (mixed, milled, and pressed) prior to thermal aging analysis are found to be between the OIT values of raw polymers and those of extracted ones. The temperature at which analysis was carried out has an influence on the polymer's OIT. OIT's are shorter at higher temperatures, increasing the maximum intensity of the CL curve and also the CL reaction rate. The activation energy (Ea) of polydienes is calculated on the basis of temperature dependency analysis. NR and BR have slightly similar Ea values of about 55 kJ/mol, while the group of SBRs, with varied vinyl or styrene content, also has similar Ea values of about 80–90 kJ/mol. PPD derivatives are anti-aging substances used to evaluate the role of antioxidants in the polymer. The consumption of antioxidant in the initial stage of the CL reaction is clearly indicated in the CL curve. Antioxidants prolong the durability of the polymer by a factor of about 3.5 to 20. DTPD is the most effective antioxidant, followed by 6PPD, IPPD, and 77PD. Thermal oxidation characterization of vulcanizates by the CL method is more complicated due to various ingredients in the mixture and to the fact that some species are fixed as pendant group in the polymer chain. This results in more than one peak in the CL curves. It is highly likely that this effect depends strongly on the type of accelerator used in the vulcanization system.

FS01.8 Substance‐specific modulation of TNF‐Alpha and IL‐1Beta in human monocytes by para‐Phenylenediamine and not by its autoxidation product Bandrowski’s Base

Para‐phenylenediamine (PPD), an arylamine dye, is a strong allergen causing allergic contact dermatitis. Cytokines such as TNF‐α and IL‐1beta are key mediators in the initiation of this reaction. Both cytokines are predominantly produced by stimulated monocytes and macroghages. We investigated the responses of PPD and Bandrowski's base (BB), an autoxidation product of PPD in human monocytes. We isolated monocytes from healthy volunteers and incubated them with the allergens. TNF‐α and IL‐1beta mRNA expression and protein levels were estimated after 45 min, 2 h, 4 h and 24 h after allergen contact. IL‐1beta and TNF‐alpha were measured in cell culture supernatants by ELISA (n = 7) and mRNA expression was determined by real‐time RT‐PCR. We found that PPD reduced TNF‐α protein secretion by 20–69.9%(n = 6). Further, IL‐1beta levels were decreased by 44–98%. The same tendency was found studying IL‐1beta and TNF‐α mRNA steady state levels (n = 3; 1 h incubation). These effects were substance‐specific and not found for PPD derivatives nor for the autoxidation product BB. These findings suggest that PPD may specifically modify immune responses by directly infering with the cellular proinflammatory cytokine network.This study was supported by the EU.

Contact dermatitis in hairdressers' clients.

The aim of our study was to report the frequency of sensitization to hairdressing allergens in a group of patients with contact dermatitis, in whom previous treatments with hair dyes or permanent wave solutions were suspected to be the cause. 49 of 261 hairdressers' clients (18.7%), who were patch tested with the hairdressers' screening series in the years 1985-1990, showed one (27) or more (22) positive reactions to hairdressing chemicals. This study confirms hair dyeing to be the procedure associated with the highest risk of sensitization among hairdressers' clients. Among hair dye allergens, PPD is the most frequent sensitizer (7.3%). A low rate of sensitization to the PPD derivatives PAP, ONPPD and PTD was detected in these clients, there being no differences in the frequency of sensitization to the 3 substances (4.2%, 4.6% and 4.6%, respectively). Only 0.4% of clients were positive to resorcinol, while pyrogallol showed a 2.3% rate of sensitization. Sensitization to GMTG was found in 3.3% of patients. ATG was an infrequent sensitizer (1.1%). Allergic contact dermatitis due to APS is quite rare (2.7%), in view of the widespread use of this compound. A positive open patch test in 1 hairdressers' client, who complained of generalized urticaria after hair bleaching, confirmed the diagnosis of immediate contact reaction due to APS. Sensitization to hairdressing allergens among consumers (18.7%) is possibly more frequent than sensitization to other cosmetic ingredients. We previously detected a 14.3% rate of sensitization to cosmetic ingredients in patients with suspected allergic contact dermatitis caused by cosmetics. On the other hand, reactions to cosmetic ingredients were also common in our patients. This may indicate that hairdressers' clients make greater use of cosmetics than average.