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Determining the effect of different drying methods on antioxidant properties in pecah kaca
(Strobilanthes crispus) leaf

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1 Norasmadi Iman Nur Sabrina, Lob Suhaizan, Mubarak Aidilla *

1 Faculty of Fisheries and Food Science, Universiti Malaysia Terengganu,
21030 Kuala Nerus, Terengganu, Malaysia.

* Corresponding author: aidilla@umt.edu.my

Abstract:
Strobilanthes crispus (S. crispus) is categorized as herbs, well-known in Malaysia and Indonesia as
“pecah beling” or “pecah kaca” where its leaves contain high antioxidant activity attributed to various
phenolic constituents, such as caffeic acid, ferulic acid, kaempferol, and luteolin. However, drying
which is a fundamental step of reducing moisture content while enhancing the shelf life of the raw
material would greatly affect the stability of the bioactive compounds and its activity. Hence, this study
was conducted to determine the effects of different drying methods, oven drying (OD), microwave
drying (MD), freeze drying (FD), and air drying (AD), on antioxidant properties of S. crispus leaves.
Total Phenolic Content (TPC) of the dried leaves extracts were determined using Folin-Ciocalteu
method and Total Flavonoid Content (TFC) were determined using aluminium chloride colorimetric
assay. Antioxidant capacities were analysed with Ferric Reducing Antioxidant Power (FRAP) and 2, 2-
diphenyl-1-picrylhydrazyl (DPPH) radical scavenging assay. S. crispus leaves dried with MD contained
significantly higher TPC (183.70±4.87 mg GAE/g), and TFC (118.70±7.49 mg QE/g) compared to the
other drying methods (p<0.05). S. crispus leaves dried with MD also showed highest value antioxidant
activity measured by FRAP (258.93±0.16 µg TE/g extract) and DPPH, (44.38±0.61% at 40 µg/ml)
when compared to the other drying methods. The inhibitory concentration (IC50) values of S. crispus
were measured and compared with the synthetic antioxidant, BHT. S. crispus dried with MD showed
the lowest IC50 value of (11.47±0.34 µg/ml), followed by leaves dried with FD (33.19±2.58 µg/ml),
AD (48.29±0.39 µg/ml), and OD (492.77±17.65 µg/ml), which were all more potent than the BHT
(52.23±7.02 µg/ml) except OD. This study illustrates a good antioxidant activity of S. crispus,
particularly when dried with MD, which can be a good candidate for utilization in the nutraceutical
industry.

Keywords: Strobilanthes crispus, Antioxidant, Drying techniques, Microwave drying, Medicinal plant