Phytochemical properties, cytotoxicity and antiviral activity of orthosiphon stamineus extracts against herpes simplex virus type 1 (hsv-1)

• Main Author: Alaa Abd Alwahid Jiheel (P74575)
• Other Authors: Nazlina Ibrahim, Dr.
• Format: theses
• Language: English
• Published: UKM, Bangi 2023
• Subjects: Orthosiphon stamineus; Phytochemical screening; Herpes simplex virus; Cytotoxicity; Antiviral; Dissertations, Academic > Malaysia
• Online Access: https://ptsldigital.ukm.my/jspui/handle/123456789/463549

The study aims at screening the antiviral potential and mechanism of action Orthosiphon stamineus (Misai Kucing) leaves and flower extracts against herpes simplex virus type 1 (HSV-1). Five extracts were prepared from O. stamineus with three extracts from the leaves using ethanol (ELE), methanol (MLE) and water (ALE) as extractants and two extracts from the flower using ethanol (EFE) and water (AFE) as extractants. Highest yield of extract was obtained in MLE (15% w/w) and the others were between 2.3 - 3.6 % w/w. Phytochemical screening revealed the presence of alkaloids, saponins, flavonoids, tannins, terpenoids, steroids and anthraquinones in ELE, MLE and EFE. Aqueous extracts (ALE and AFE) showed the presence of flavonoids, tannins and terpenoids only. No cytotoxicity towards Vero cell was noted from all the extracts with cytotoxic concentration that causes 50% of cell death (CC50) values ranging between 2 to 7.4 mg/mL. The antiviral activity against HSV-1 was determined using plaque reduction assay with selectivity indices (SI) between 18 to 31 indicating good potential as antiviral agent. For the mechanism of action studies, pretreatment of extracts to Vero cells before virus inoculation did not show any effect on virus infectivity indicating that the extracts did not have any impact on Vero cells. In the virucidal assay, all the extracts were incubated with HSV-1 for 30 minutes prior to infection. All the extracts have modified virus structure that causes failure in the adsorption or entry into host cells that was indicated by inhibition in plaque formation. This is confirmed by different degrees of inhibition in attachment and penetration assays. In the virus yield assay, virus infected cells were treated with different concentration of MLE for more than 24 hours after which titration of released virus was done. Plaque formation was inhibited at 52.1%, 53%, 64% and 73.2% at 0.05, 0.1, 0.15 and 0.2 mg/mL respectively. These results confirmed the notion that MLE contains active components that interfere with intracellular activity of the virus. Finally, both time addition and time removal assay were performed to investigate the time point of MLE to affect viral infectivity or how much time required by extract to completely eradicate the virus. The results showed that MLE can affect virus at all replication stages due to plaque inhibition that was noted at every time point tested beginning from 2 hour post treatment until 12 hours in time of addition assay and 30 hours in time of removal assay. This study demonstrated that O. stamineus extracts have good antiviral activity with potential for the development as antiherpetic agent that can affect many stages of viral replication but not as prophylaxis.,Certification of Master's/Doctoral Thesis" is not available