No abstract

Drug development for neurodegenerative diseases (NDs) is foremost task for the medicinal chemists in the 21st century. Coumarins are exemplary of an assorted and aptitudinally useful set of drugs. Coumarins play a momentous role in several pharmacological and medicinal aspects. Its analogues are anticipated to play a significant role in the development of new therapeutic leads for NDs. Their promising applications in the field of ND medication are exemplified by clinical candidates such as nodakenin that have been potent for demoting memory impairment. Apart from ND, clinically used anticoagulant warfarin, anticoagulant dicoumarol, and antibiotic coumermycin, novobiocin and chartesium grab the interest of researchers in coumarins. It would be worthwhile to look at the different biological processes that could cause neurodegeneration, thereby establishing a link with distinct coumarin derivatives to serve the purpose of medication. This review undertakes estimation of the wide spectrum of studies focusing coumarin to the domain of drug research for ND. Herein, we search for multitarget coumarin‐based inhibitors and their scope for NDs. Future challenges in coumarin‐based drug development have been discussed, and emphases have been laid on the future perspectives of coumarins as possible drugs in the future for the treatment of NDs.

No abstract

No abstract

No abstract

We investigate strong field gravitational lensing by rotating Simpson-Visser black hole, which has an additional parameter (0 ≤ l/2M ≤ 1), apart from mass (M ) and rotation parameter (a). A rotating Simpson-Visser metric correspond to (i) a Schwarzschild metric for l/2M = a/2M = 0 and M = 0, (ii) a Kerr metric for l/2M = 0, |a/2M | < 0.5 and M = 0 (iii) a rotating regular black hole metric for |a/2M | < 0.5, M = 0 and l/2M in the range 0 < l/2M < 0.5 + (0.5) 2 − (a/2M ) 2 , and (iv) a traversable wormhole for a |a/2M | > 0.5 and l/2M = 0. We find a decrease in the deflection angle α D and also in the ratio of the flux of the first image and all other images r mag . On the other hand, angular position θ 1 increases more slowly and photon sphere radius x m decreases more quickly, but angular separation s increases more rapidly, and their behaviour is similar to that of the Kerr black hole. The formalism is applied to discuss the astrophysical consequences in the supermassive black holes NGC 4649, NGC 1332, Sgr A* and M87* and find that the rotating Simpson-Visser black holes can be quantitatively distinguished from the Kerr black hole via gravitational lensing effects. We find that the deviation of the lensing observables ∆θ 1 and ∆s of rotating Simpson Visser black holes from Kerr black hole for 0 < l/2M < 0.6 (a/2M = 0.45), for supermassive black holes Sgr A* and M87, respectively, are in the range 0.0422-0.11658 µas and 0.031709-0.08758 µas while |∆r mag | is in the range 0.2037-0.95668. It is difficult to distinguish the two black holes because the departure are in O(µas), which are unlikely to get resolved by the current EHT observations, and one has to wait for future observations by ngEHT can pin down the exact constraint. We also derive a two-dimensional lens equation and formula for deflection angle in the strong field limit by focusing on trajectories close to the equatorial plane.

We study gravitational lensing in strong-field limit by a static spherically symmetric black hole in quartic scalar field Horndeski gravity having additional hair parameter q, evading the no-hair theorem. We find an increase in the deflection angle $$\alpha _D$$ α D , photon sphere radius $$x_{ps}$$ x ps , and angular position $$\theta _{\infty }$$ θ ∞ that increases more quickly while angular separation s more slowly, but the ratio of the flux of the first image to all other images $$r_{mag}$$ r mag decreases rapidly with increasing magnitude of the hair q. We also discuss the astrophysical consequences in the supermassive black holes at the centre of several galaxies and note that the black holes in Horndeski gravity can be quantitatively distinguished from the Schwarzschild black hole. Notably, we find that the deviation $$\Delta \theta _{\infty }$$ Δ θ ∞ of black holes in Horndeski gravity from their general relativity (GR) counterpart, for supermassive black holes Sgr A* and M87*, for $$q=-0.2$$ q = - 0.2 , respectively, can reach as much as $$2.4227~\mu $$ 2.4227 μ as and $$1.82026~\mu $$ 1.82026 μ as while $$\Delta s$$ Δ s is about $$0.04650~\mu $$ 0.04650 μ as for Sgr A* and $$0.03493~\mu $$ 0.03493 μ as for M87*. The ratio of the flux of the first image to all other images suggest that the Schwarzschild images are brighter than those of the black holes in Horndeski gravity, wherein the deviation $$|\Delta r_{mag}|$$ | Δ r mag | is as much as 0.70673. The results suggest that observational tests of hairy black holes in Horndeski gravity are indeed feasible. Taking the supermassive black holes Sgr A* and M87* as the lens, we also compare our hairy Horndeski black holes observable signatures with those of the neutral Horndeski black holes, Galileon black holes and charged Horndeski black holes. It turns out that although it is possible to detect some effects of the strong deflection lensing by the hairy Horndeski black holes and other black holes with the Event Horizon Telescope (EHT) observations, but it is unconvincing to discern these black holes as deviations are $${\mathcal {O}}(\mu $$ O ( μ as). We also find that the shadow size is consistent with EHT observation if the deviation parameter $$q \in (-0.281979,0)$$ q ∈ ( - 0.281979 , 0 )

No abstract