The objective of this present study is to focus on the in silico study to screen for an alternative drug that can block the activity of the angiotensin converting enzyme 2 (ACE2) as a receptor for SARS-CoV-2, potential therapeutic target of the COVID-19 virus using natural compounds (Isothymol, Thymol, Limonene, P-cymene and c-terpinene) derived from the essential oil of the antiviral and antimicrobial plant Ammoides verticillata (Desf.) Briq. which is located in the occidental Algeria areas. This study reveals that Isothymol, a major component of this plant, gives the best docking scores, compared to, the co-crystallized inhibitor b-D-mannose of the enzyme ACE2, to Captropil drug as good ACE2 inhibitor and to Chloroquine antiviral drug also involved in other mechanisms as inhibition of ACE2 cellular receptor. In silico (ADME), drug-likeness, PASS & P450 site of metabolism prediction, pharmacophore Mapper showed that the compound Isothymol has given a good tests results compared to the b-Dmannose co-crystallized inhibitor, to Captopril and Chloroquine drugs. Also the other natural compounds gave good results. The Molecular Dynamics Simulation study showed good result for the Isotymol-ACE2 docked complex. This study revealed for the first time that Isothymol is a functional inhibitor of angiotensin converting enzyme 2 activity and the components of essential oils Ammoides verticillata can be used as potential inhibitors to the ACE2 receptor of SARS-CoV-2. ARTICLE HISTORY

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The oxidative addition of PhI to [Pd0(PPh3)4] in DMF is slower when performed in the presence of the terminal alkynes (PhC≡CH, EtO2C−C≡CH) that are reagents in palladiumcatalyzed Sonogashira or multicomponent reactions. The concentration of the reactive [Pd0(PPh3)2] complex decreases because of its partial coordination to the alkyne to form [(η2‐RC≡CH)Pd0(PPh3)2] (R = Ph, EtCO2), which is in equilibrium with [Pd0(PPh3)2]. The complex [(η2‐PhC≡CH)Pd0(PPh3)2] was found to be unreactive whereas [(η2‐EtO2C− C≡CH)Pd0(PPh3)2] was found to be the unique reactive complex at high concentrations of EtO2C−C≡CH. As has been reported for alkenes, terminal alkynes play an unexpected role because they interfere in the oxidative addition before their usual reactions in the carbopalladation and transmetallation steps that follow it. Decreasing the rate of the fast oxidative addition with PhI may promote the efficiency of the catalytic cycle by bringing its rate closer to that of the slower carbopalladation or transmetallation steps. (© Wiley‐VCH Verlag GmbH & Co. KGaA, 69451 Weinheim, Germany, 2004)

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