Voltage is usually lowered with resistor and internal resistance of unipolar capacitor which doesnt develop heat like resistors. This design is up to 100mA after that you need bigger capacitor, then better use transformer. You can search EDABoard threads recently was several good threads about this topic.
But you can see some examples for higher amperage :
If your 230 V AC is the power main, then "reducing the AC voltage" without a transformer is VERY DANGEROUS!
The small and low-cost 230V/ 5 V AC transformers are built with a good safety insulation.
You can replace such transformer with capacitors or resistors to get ~5 V AC but the output current is low (several mA) and you can get a good shock by discharging such capacitor.