Preparation of pyridopyrazines through tandem Pd-catalyzed C-N/C-C coupling reactions of Ugi adducts.

A Pd-catalyzed selective tandem cyclization of the Ugi adduct via Buchwald-Hartwig/C-H bond functionalization reactions has been reported. This sequence offers an interesting approach for synthesizing a wide range of pyrido[1,2-a]pyrazine-3,6-dione scaffolds under mild reaction conditions in moderate to excellent yields. The scope and limitations of the protocol are discussed.

Incensole derivatives from frankincense: Isolation, enhancement, synthetic modification, and a plausible mechanism of their anti-depression activity.

Encouraged by the potent anti-depression activities of incensole (1) and incensole acetate (2) isolated from the resin of Boswellia papyrifera in our previous work, different derivatives of 1 and 2 were synthesized in the present study. The reaction of 1 with m-CPBA afforded the mono-epoxide derivative 3a, while the same reaction with 2 led to three different epoxide derivatives 3a, 3b, and 3c. Oxidation of 1 with PCC to get compound 3b, however along with the target 3b, the reaction gave three interesting side products (3c-3e). Oxime (3b-1) resulted from the reaction of 3b with hydroxylamine hydrochloride in pyridine, while epoxidation of 2 generate three epoxide products (4a-4c). The structures of all products were unambiguously confirmed using NMR and Mass spectrometry. Compounds 3a-e and 4a-c (0.1-3 mg/kg, i.p.) demonstrated promising anti-depression activities in classical mouse models of depression of FST and TST. The results showed that compounds 3a-e and 4a-c (0.1-3 mg/kg, i.p.) caused dose dependent reduction in immobility time compared to the vehicle control, with 3c-3e and 4b-4c demonstrating higher potency and efficacy. The findings of the open field test excluded the motor effects of these compounds, thus further confirming their anti-depression activity. Preliminary investigation into their mechanism of action using GABA antagonist, PTZ and molecular docking has predicted that compounds 3e and 4c bind at the GABA binding site of GABAA receptor to produce GABAergic effects. Furthermore, the promising anti-depression potency of compounds 1 and 2 and their derivatives make them lead compounds for drug discovery.

New derivatives of 11-keto-ß-boswellic acid (KBA) induce apoptosis in breast and prostate cancers cells.

A series of new 11-keto-ß-boswellic acid were partially-synthesized by modifying the hydroxyl and carboxylic acid functional groups of ring A. The structures of the new analogs were confirmed by detailed spectral data analysis. Compounds 4, 5 and 9 exhibited potent anti-cancer results against two human tumor cancer cell lines having IC50 value of MCF-7 (breast) and LNCaP (prostate): 123.6, 9.6 and 88.94 µM and 9.6, 44.12 and 12.03 µM, respectively. Additionally, a maximum nuclear fragmentation was observed for 4 (78.44%) in AKBA treated cells after 24 hr followed by 5 and 9 with (74.25 and 66.9% respectively). This study suggests that the presence of hydrazone functionality (4 and 9) has effectively improved the potency of AKBA. Interestingly, compound 5 with a lost carboxylic acid group of ring A showed comparable potent activity. Highly selective AKBA requires further modification to improve its bioavailability and solubility inside the cancer cells.

Synthesis of new boswellic acid derivatives as potential antiproliferative agents.

In the current investigation, a series of heterocyclic derivatives of boswellic acids were prepared along with new monomers of 3-O-acetyl-11-keto-ß-boswellic acid (AKBA, 1) 11-keto-ß-boswellic acid (KBA, 2) and several new bis-AKBA and KBA homodimers and AKBA-KBA heterodimers. The effects of these compounds on the proliferation of different human cancer cell lines, viz., FaDu (pharynx carcinoma), A2780 (ovarian carcinoma), HT29 (colon adenocarcinoma), and A375 (malignant melanoma), have been evaluated. Thus, KBA homodimer 21 effectively inhibited the growth of FaDu, A2780, HT29, and A375 cells with EC50 values below 9 µM. In addition, compounds 7, 8, 11, 12, 15, 16, and 17 also exhibited cytotoxic effects for A2780, HT29, and A375 cancer cells. In particular, the pyrazine analog 8 was highly cytotoxic for A375 cancer cells with an EC50 value of 2.1 µM.

Evidence for the involvement of a GABAergic mechanism in the effectiveness of natural and synthetically modified incensole derivatives in neuropharmacological disorders: A computational and pharmacological approach.

In the course of our continuing exploration for novel bioactive lead compounds (s) from the species Boswellia, we have recently reported incensole derivatives isolated from Boswellia papyrifera Hochst. Given the known antidepressant-like effects of incensole and incensole acetate, we herein present that the low dose intraperitoneal administration of incensole derivatives, namely, incensfuran and incensone, showed significant antidepressant-like effects in the forced swim test (FST) and tail suspension test (TST). Furthermore, these compounds were evaluated for their anxiolytic potential in the elevated plus maze (EPM) and light dark box (LDB) tests and anticonvulsant effects in pentylenetetrazole (PTZ)-induced seizure tests. In the EPM test, administration of these compounds led to dose-dependent increases in open arm entries and in the time spent in EPM open arms. Similar results were obtained in the LDB test, wherein compounds these caused significant increases in the number of transitions between lit and dark compartments and the time spent in the lit compartment. The anxiolytic-like effects in the EPM were not reversed by pretreatment with flumazenil, whereas PTZ and bicuculline (BIC) completely abolished the anxiolytic effects, showing the involvement of the non-benzodiazepine binding sites of GABAA receptors. All four compounds induced significantly elevated brain GABA levels, indicating the involvement of a GABAergic mechanism. Additionally, molecular docking was conducted to elucidate the mode of action for the anxiolytic and anticonvulsant effects of these derivatives. Moreover, these compounds also possess drug-like properties and excellent ADMET profiles.

Quantification of Incensole in Three Boswellia Species by NIR Spectroscopy Coupled with PLSR and Cross-Validation by HPLC.

INTRODUCTION: Incensole can be considered as a biomarker for Boswellia species which is a diterpene that has received remarkable pharmacological interest recently due to its potent anti-inflammatory and anti-depressant activity. OBJECTIVE: Near-infrared (NIR) spectroscopy coupled with PLSR (partial least squares regression) as a robust, rapid and alternative method was used to quantify the content of incensole in three species namely B. papyrifera, B. sacra and B. serrata and cross-validated by high-performance liquid chromatography (HPLC). MATERIALS AND METHODS: NIR spectrophotometer was used for the quantification of incensole standards and Boswellia species in absorption mode in the wavelength range between 700 and 2500 nm. A PLSR model was built from the obtained spectral data using 70% of the incensole working standard solutions (training set), ranging from 0.5 to 100 ppm. The PLSR model obtained has a R2 value of 98% with a correlationship of 0.99 and a good prediction with root mean square error for prediction (RMSEP) value of 3.2%. RESULTS: The results indicated that the methanol (MeOH) extract of B. papyrifera resin has the highest concentration of incensole (18.4%) followed by n-hexane (13.5%) and ethyl acetate (3.6%) while trace amounts was detected in the fractions of B. sacra and no incensole was detected in the fractions of B. serrata. CONCLUSION: The findings are in total agreement with the HPLC analysis suggesting that NIR spectroscopy coupled with PLSR is a robust, rapid and non-destructive alternate method for the quantification of incensole in B. papyrifera. Copyright © 2018 John Wiley & Sons, Ltd.